3.    Planning and tracking your diet

3.1  What is a calorie?

Let’s start with the calorie which is a unit defined by physicists as a measurement of energy. At its simplest 1 cal (with a small “c”) is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius.  Equally 1 cal represents the amount of energy that would have to be removed from 1 gram of water to reduce its temperature by 1 degree Celsius.  It can be used to represent the energy the body can produce from our food via the process of metabolism, but it can equally be used to represent the energy we expend (which is another way of saying “the work we have done”) in running up a flight of stairs.

In practice, 1 cal represents quite a small amount of energy so another unit has evolved for use when describing energy levels for human exercise or the energy obtained from food consumption, hence :

1 Cal (with a capital “C”) = 1000 cals (with a small “c”)

Food labels now tend to avoid the use of “Cal” as it can be confusing so you will normally find that the unit Cal is has been almost entirely replaced by kcal where 1 kcal = 1000 cals = 1kcal.

The recommended daily intake of energy from food is 2400 kcals for an “average” male and 2000 kcals for an “average” female.  There are slight variations on this recommendation with age but these are a good starting point when determining if you are eating too much or too little.

3.2   How excess calories become stored as fat

At the most simplistic level our food input and its conversion through metabolism to energy our body can use can be considered to be just an energy balance : Energy in = Energy out.  Or put another way, if you consume more calories than you need for your energy expenditure you will store the surplus as fat, which implies that to lose weight all you need to do is  “Eat less and exercise more”.

While that simplistic statement may be generally true (we all know that eating too much will probably increase our weight), it is very much an over simplification because the type of food we eat has an influence on whether fat storage will be triggered, as well as the amount of calories consumed.   In addition our gut bacteria and hormones also play a part in regulating our fat storage.

Fat storage is triggered by the hormone insulin, rather than directly by the calories consumed in our food, which is why simple calorie counting may not give you the fat loss you desire.    That is because all foods  are not equal when it comes to their affect on insulin levels :  foods which raise insulin levels may well trigger fat storage if we cannot immediately use up the available energy, whereas foods that have minimal impact on insulin levels do not trigger fat storage. This is a key point in understanding how any weight loss programme works.  Get this wrong and you could easily cut calories, become undernourished, yet still continue to add weight in the form of fat!

Meat and protein have virtually no effect on raising insulin levels so are unlikely to lead directly to increased fat storage, but the refined starchy carbohydrates and sugars that abound in modern day processed food and snacks can have a very dramatic effect on our blood sugar and insulin.   Eating less of these foods, or eliminating them entirely as I did by adopting a Mediterranean style of food, can have a huge effect on the level of fat storage.  So the guidance to “Eat less and exercise more …” should really be more specific :  “Eat less of the refined starchy carbohydrates and sugar that cause an abnormal rise in insulin levels and leads directly to fat storage, and exercise more”.   For a weight loss diet to be successful you need to turn off the fat storage mechanism by eating the right kind of foods in appropriate quantities and you need to make the dietary change permanent if you want to maintain that weight loss.

But we are all individuals, and fat storage depends on more than just  calories and food types.  Tim Spector points out in “The Diet Myth” that genes and the makeup and health of the microbes in our  microbiome can determine that identical twins eating the same diet and exercising similarly can develop with one thin twin and one obese twin.

So the amount of food consumed, the type of food consumed, our genes, and our gut bacteria all interact in a complex way to influence fat storage in our bodies.  While there is no single set of rules that is guaranteed to work for everyone, there are nevertheless a number of factors that can utilize to influence your individual fat storage or. You just need to understand what works best for you.

How does fat storage actually arise in the body?  When you consume carbohydrate the small intestine metabolizes the food to extract the energy it contains which is then transported through the body via an increase in our blood glucose levels.  The level of blood glucose is controlled by insulin, a hormone produced in the pancreas, which causes excess blood glucose to be initially re-directed to storage as glycogen in the muscles and liver.   The amount of surplus energy that can be stored as glycogen is limited, but this energy is available for rapid release when required.  However, once the glycogen storage limit has been reached, surplus energy is then destined for long term storage as fat, which is generally deposited around the belly in men and around the thighs and buttocks in women.

So our pancreas produces insulin as a response to elevated levels of glucose in the blood, and elevated blood sugar is generally the result of eating carbohydrates (particularly "fast" carbs) since fat and protein have minimal effect on blood sugar. Over time, eating too much sugar and starchy carbohydrates can lead to “insulin resistance” or “metabolic syndrome” where the muscle cells no longer respond fully to the insulin.   At this point average blood sugar levels start to rise and this is the precursor for Type 2 Diabetes.

The bottom line is that if you regularly eat a lot of sugar, starchy carbohydrates, or refined carbohydrates, more than you need for your immediate energy needs, then the excess energy you consume will be destined for storage.   The glycaemic index of a food indicates how that food will raise the level of blood sugar by comparison to pure glucose, which has a GI value of 100.   Foods with a GI above 50 are considered to be of high GI.   Pure sugar and many starchy carbohydrates are of high GI but not all carbohydrates are of high GI.  Whole grains generally take much more time to be digested and consequently have a low GI value.  If you have an elevated blood sugar level like I had, then sugar, refined carbohydrates, and starchy carbohydrates need to be reduced or eliminated from your diet, while whole grain carbohydrates and carbohydrate from vegetables and most fruits, can continue to be eaten.  However carbohydrates are generally of high calorie density (i.e. lots of kcals per gram of food) so you still need to be conscious of how much you are eating if you want to lose weight).

The conversion of excess calorie intake to storage as glycogen or fat can happen within four to eight hours of starting a meal.  Initially the liver and muscles mop up any excess calories but they are limited, in total, to about 1000 kcals of storage.  Once they have reached their maximum glycogen storage then any excess calories are stored as triglycerides within our fat cells – we begin to accumulate body fat for long term storage.

Those surplus calories are converted to fat at the rate normally specified as 1kg of fat per 7700 kcals, although this conversion factor is very much a simplification, and is the subject of some dispute.  You should treat 7700kcals/kg fat as a starting point for “what-if” estimates to estimate what you need to do in your diet, because the type of food is probably much more significant than the quantity of calories consumed.   Nevertheless, by diligent tracking of everything I ate and all the exercise I did over a six month period, I found that that there was a very close correlation between the reduction in calories from starchy carbohydrates, my actual weight loss, and the conversion factor of 7700 kcals per kg of fat.   So for me the simple energy balance actually worked, but that may not be the case for everybody.

The body will always prefer to get a quick energy fix from carbohydrates rather than convert fat to glycogen which can then release energy to our cells.   So even if our glycogen storage is full and we have ample stored fat, a burst of exercise could leave you feeling temporarily hungry because the body will always prefer to grab a sugary carbohydrate in preference to converting stored fat to energy.  In order to start burning fat you have to raise your exercise levels significantly for an extended period of time.   The bottom line is that you can accumulate fat much easier than you can burn it off!

I have not found any simple way of calculating how long it takes the body to start burning fat because there are so many variables.  If you simply fast then it may take 12 hours or more for the body to begin converting the fat cells to provide energy but if you hit the treadmill and exercise in the “fat burn” zone, where your heart rate is significantly elevated, then fat burn will be triggered much more readily.  That is why a combination of calorie restriction and cardio exercise will provide the optimum approach to fat loss.

3.3   Are all calories equal when it comes to creating stored fat?

Definitely not!   We have seen in the previous section that the "fast" carbs like sugars and refined carbohydrates have the greatest effect on our blood sugar and insulin levels, and hence their tendency to increase fat storage, but we need to look at this in a bit more detail as there are additional factors to consider.

At the most basic level the metabolic processes which break down the food to release its energy require finite energy to function so that the net energy extracted and made available to the body will always be slightly less than the calorific value of the food consumed.  Some foods are metabolized easily and quickly so almost all their energy becomes rapidly available, while others require much more work to break them down which results in less total energy becoming available to the body and spread over a longer time.   That means that two foods with exactly the same  calorific value (expressed in kcals on a food's nutrition label) may differ substantially in the actual amount of energy released to the body through metabolism as well as  the time over which that energy is made available.   This discrepancy arises because the calorific value on food labels (in kcals/100g) is measured using a device called a “bomb” calorimeter which makes no allowance for metabolic processes or the variation in these between individuals caused by our microbiome.   The bomb calorimeter simply measures the energy released when the food is burned completely in an oxygen environment.

So the maximum energy our bodies can actually extract from different foods will vary somewhat from calorific value expressed on a food label and it will always be less than the stated value, although the difference may be small in practice.   In addition, the time it takes for our metabolic processes to break down the food can vary substantially so that energy from one food may be released rapidly while another is released slowly.

In this thought provoking video : http://www.theobesityepidemic.org/2014/02/a-calorie-is-not-a-calorie-and-heres-the-reason-why/  Dr Zoe Harcombe explains that about 93% of the energy in a carbohydrate can be extracted by the body whereas for protein the figure is only around 73%.  That means that most of the energy in carbohydrate becomes available to the body whereas only about three quarters of the energy in protein can be usefully extracted.  Although she does not mention this in the video, fats are actually worse than carbohydrates in this regard as about 97% of the energy they contain can be extracted through metabolism, although the breakdown process is slower than for carbohydrates or protein so fats do not cause any significant increase in blood sugar levels.  In fact carbohydrates are metabolized fastest followed by protein and then fat.  Alcohol, which is definitely not a macro nutrient as it provides only empty calories of no nutritional value, gives up only about 80% of its inherent energy of 7kcals/gram through metabolism.   It does however have a high energy density so, even although it may not be processed efficiently by the metabolism, it should still be avoided on a diet!

Dr Harcombe’s video also makes the claim that the energy required to support our basic metabolic processes at rest, the Basal Metabolic Rate or BMR, can only come from fat and protein, not carbohydrates, which I consider to be a very profound statement and something new to me. I confess I find her statement to be a bit baffling and cannot find a lot of supporting information to back it up.  It is very significant as the BMR comprises about  70% of our daily needs so if she is right, and I have no reason to doubt it, we need to factor in that the BMR needs should be delivered by fat and protein and calorie restriction should look at the balance between the BMR and your actual daily energy requirement as defined by your level of activity and exercise.  This is certainly a radically different way of thinking and not what I did for my diet where I calculated total daily energy requirements and how much calorie restriction needed to take place overall in order to achieve weight loss.

Fortunately I cut my consumption of calories from starchy carbohydrates by about 50% so my fat and protein intake went up proportionately to compensate.   However, had I chosen to drastically restrict fat and protein rather than carbohydrates then, according to Dr Harcombe,  my diet outcome may have been completely different and rather less spectacular.   I may have ended up with rather unhealthy results, as in her video she shows what happens if you over eat carbohydrates and under eat protein and fat - leading to insufficient energy to meet the needs of your Basal Metabolic Rate yet still putting on weight!

What would this actually mean for me in numbers?  Using the concept of Metabolic Equivalents (METs), which we will return to later when we look at exercise levels in Section 7.2, I can calculate my Basic Metabolic rate simply as 1 kcal/hour per kg of body weight.   Since I weigh 68kg this means that my BMR is 68 kcals/hour, which means that I need 1632kcals every 24 hours just to support basic body functions in a completely rested state.  The TDEE calculator referred to in section 3.4 below estimates a value of 1721kcals, but that calculation uses a lot more data that is specific to me rather than the simple generic MET equation.  Either way I need around 1700kcals per day just to keep the body functioning at rest and Dr Harcombe suggests  that these calories need to come from fat and protein, not carbohydrate.   What I did worked for me but you should discuss any significant dietary changes first with your doctor.

Hopefully we now have a better understanding that cutting calories is not quite so simple as eating less and exercising more.  We need to cut the right kind of calories to prevent fat storage but even if we do that, the microbes that constitute our microbiome and our hormones can also significantly influence how fat is stored burned.  Lastly, our metabolic processes require energy to break down our food, so fat, carbohydrate, and protein all give up a different proportion of their “label” calories.   Here is a summary of the main points :

·         Consuming carbohydrates raises our blood sugar, causing the pancreas to release insulin to regulate the blood sugar back to safe levels.  This regulation of blood sugar is a normal process in the body but can be impaired by eating too many sugars and starchy carbohydrates (the "fast" carbohydrates).

·         Eating wholegrain unprocessed carbohydrates with a low glycaemic index will not have an adverse affect on blood glucose level if eaten in moderate quantities (“moderate” is typically defined as 50g dried wholegrain per portion).   Similarly eating "green" carbohydrate from vegetables and most fruits will not have an adverse affect on blood sugar because the high level of fibre in these foods significantly slows down their absorption in our digestive tract,

·         Eating sugars and starchy carbohydrates (the "fast" carbohydrates) can have an adverse effect on insulin levels and fat storage that is disproportionate to the quantity of calories they contain, and much more so than would be predicted from the simple energy balance equation.

·         Fat and protein have negligible effect on insulin levels and consequently have minimal effect on fat storage (although, as explained in the Section 3.4 below, the combination of eating fat with starchy carbohydrates or sugars should be avoided as it can lead to a rise in blood sugar caused by the fat).

Fats, proteins, and carbohydrates all require different amounts of energy to be broken down by our metabolism, which means that not all of their calorific value becomes available to the body.  Unfortunately carbohydrates give up almost all their stated calorific value.  The maximum energy that can be extracted by metabolism from the stated calories in fat, carbohydrate, protein, and alcohol is 97%, 93%,73%, and 70% respectively, which gives protein a significant metabolic advantage if you are trying to lose weight (but speak to your doctor before you drastically change your protein consumption!).   Fat gives up the highest proportion of calories when metabolized but these do not influence fat storage as explained above.

In the typical Western diet we are now consuming more refined carbohydrates and sugars than we have ever done in history, which is perhaps an unforeseen consequence of the advice to eat low fat diets which has caused us to increase in our carbohydrate intake, and particularly refines carbohydrates.  Fat has a high calorie density, is almost fully metabolized by the body, but it nevertheless has a low glycaemic index because it cannot be metabolized quickly.  Since the Mediterranean Diet is based on lots of fruit, vegetables, nuts, and olive oil which are all inherently of low glycaemic index, it will have minimum impact on blood sugar levels, and consequently is less likely to lead to fat storage if you occasionally over indulge.  Long term of course, if you eat significantly more calories than you need for your general level of daily activity then you will probably gain weight.

3.4   Food combinations and fat storage

Diets based on certain food combinations have been around for a long time and are based on the ideas of (a) not eating fast and slow digesting foods at the same time (e.g. fruit and fat) and (b) not combining foods that require different  pH or acidic levels for the digestive enzymes to work effectively.

From what I've read, there is no scientific evidence to substantiate the two premises on which this food combination theory is based, and in fact the science generally contradicts the claims.   Our gut seems perfectly able to handle foods that digest at different rates and it is also perfectly able to maintain different levels of pH in different regions to suit the digestive enzymes.  Eating food which is alkaline or acidic does not affect the underlying pH of the digestive tract because the body regulates the pH automatically.

However I did come across several references suggesting that the combination of eating  fat with starchy carbohydrates or sugar should be avoided, but for reasons that are unrelated to the standard food combination theory mentioned above.  While insulin is the main hormone that controls the storage of fat, there are two other hormones that can also cause fat to be stored.  The Glucose-Dependent Insulinotrophic Peptide (GIP) hormone is influenced by both carbohydrates and fat and not only causes fat to be stored but causes more insulin to be released as well.  However the effect of GIP is minimal if the blood sugar level is low or normal.   In other words eating fat releases GIP but the effect on insulin levels, blood sugar, and hence fat storage is minimal if the blood sugar is already low or normal.   However if the blood sugar is raised, by eating starchy carbohydrates for example, then the effects of GIP are amplified considerably and can lead to fat storage that is much higher than eating either the fat or carbohydrate alone.

Another hormone called Acylation Stimulating Protein (ASP) is also influenced by fat but also by insulin and hence indirectly by carbohydrates.  Like GIP, the combination of eating fat and carbohydrates can cause ASP to trigger fat storage.

The GIP and ASP hormones are yet another reason why all food calories are not equal when it comes to creating fat storage and why simple calorie counting may not give you the result you expect   Unfortunately for  us the combination of fat and starchy carbohydrates/sugar produces some wonderfully tasty combinations like ice cream and hamburger and chips!  If you are in true calorie deficit then the effects of such foods may be minimal, but it is equally possible that you could cut calories yet fail to lose any weight if you eat a diet rich in fat, sugar and starchy carbohydrates.   In my case the proportion of fat in my Mediterranean diet increased substantially but I also eliminated all free sugar and starchy carbohydrates and restricted my overall calories to about 1600 kcals/day.

I will close this section with some fascinating insights from James Wong's superb book "How to eat better" in which he explains the science behind how certain food combinations can enhance the quality of the foods you eat.  For example :

·         Eat black beans with rice to suppress the rise in blood sugar that you would otherwise experience from rice alone.

·         Increase the quantity of fat soluble beta carotene, which is a precursor for producing vitamin A in the body, by cooking carrots rather than eating them raw.  And if you add olive oil, then you can increase the beta-carotene another 50%.

·         Store tomatoes outside the refrigerator to increase the quantity of the phytonutrient lycopene and if you cook them, particularly in olive oil, then the absorption of lycopene in the body is increased.

·         Broccoli contains glucosinolates which have been shown to help reduce the risk of cancer and heart disease but once broccoli has been harvested it quickly loses these beneficial nutrients.   In fact up to 80% may be lost by the time broccoli reaches the shops so the fresher you can buy the better.  In addition, broccoli contains another important group of chemicals called isothiocyanates.   Cooking broccoli almost completely destroys the enzyme which makes these chemicals absorbable by the body but a dressing of mustard powder, olive oil, and lemon juice applied to cooked broccoli completely negates the negative effects of cooking.

·         Blueberries and strawberries are full of beneficial antioxidants and anthocyanins but eating them with yogurt for breakfast may not be such a good idea as milk protein has been found to prevent the absorption of these beneficial chemicals by the body.

·         Eating berries, particularly strawberries and raspberries, with carbohydrate and fat rich food can reduce the insulin response and hence the potential for fat storage.

Leave button mushrooms on a sunny window sill for a couple of hours and their level of vitamin D can be increased a hundredfold.

There are loads of other science based tips and recommendations in his book which I highly recommend.

3.5   Estimating your daily calorie requirements

If you cut just a few hundred calories from your normal daily consumption you will eventually lose weight, but if you want to be a bit more in control of the process and how long it might take then you need to start by estimating how many calories you actually need every day.  One measure of this requirement is the Resting Metabolic Rate which defines how many calories you need just to cover the basic metabolic processes.  However the RMR just defines the minimum energy needed to support the basic metabolic processes and does not represent a typical day (unless of course you spend it in bed!).   Note that the Resting Metabolic Rate and the Basal Metabolic Rate are very similar and tend to be used interchangeably.  The BMR has a more precise definition than the RMR but for practical purposes of dieting this can be ignored.   I calculated my BMR above in Section 3.3 using the definition of Basic Metabolic rate simply as 1 kcal/hour per kg of body weight.

A better measure for calorie restriction planning is the Total Daily Energy Expenditure (TDEE) which factors in a certain amount of physical activity along with your age, weight, height, and fat content if known.  I used this calculator :  https://tdeecalculator.net to estimate my basic requirements.

Feeding in my parameters at the start of my diet [male; age 63; height 174cm; weight 85.5kg; fat level 29.5%] along with the “light exercise” option gave me a TDEE of  2367 kcals/day.  So eating less than 2367 kcals per day, or increasing the level of exercise, should cause weight to be lost, providing I also modified my diet to eliminate simple carbohydrates and sugars which can lead to excessive fat storage.   How do you calculate how many fewer calories you need to eat to lose a certain amount of weight?  Read on!

3.6   Relationship between fat, calories consumed, and weight loss

We have seen in the previous sections that  “Eating less and exercising more” may not do it for everyone and that all calories are definitely not equal when it comes to predicting fat loss through calorie restriction.    Individuals vary too in their metabolism and microbiome, so how on earth can you plan a weight loss programme?

Fat gain, for most people,  is simply the result of eating too many calories, and that fat gain can be significantly enhanced by eating too many of the wrong kind of calories, specifically sugar and refined carbohydrates, or by eating too much fast food that combines a lot of fat, sugar, and refined carbohydrates.    I found, through accurate monitoring of calories from food input and cardio exercise, that my weight loss was actually very predictable from the Energy Input = Energy Output equation using  the notional equivalence of 7700kcals per kg of fat lost.   However I think that there are five key factors that influenced my successful outcome :

(1) I turned off the principal fat storage mechanism in the body by eliminating all free sugars, starchy carbohydrates, refined carbohydrates, and any junk food.

(2) I continued to eat complex carbohydrates (whole grains, beans, lentils etc) but I did not combine these to any significant extent with fat so that the far storage effects of the GIP and ASP hormones were minimized.

(3) I significantly increased my consumption of fat and protein.

(4) I significantly restricted my daily calories on two Fast days each week and by a much more moderate amount on Feast days.

(5) I augmented by about 30% the calorie restriction from food intake with cardio exercise on at least four days per week.

In essence I turned off fat storage and encouraged fat burning, and was able to achieve a weight loss that was consistent with approximately 1kg of fat loss for each 7700 kcals of deficit over the six month period.  However I am quite sure that if I had restricted calories but continued to eat simple carbohydrates and sugar then the simple energy balance equation would not have worked nor would I have lost so much weight.

For a calorie restricted diet then “Energy Input” must of course be less than “Energy Output” but how much weight can you expect to lose?   Let’s put this into some kind of context.   Given the caveats and key factors above then for me it worked out that 1kg of body fat could be considered to represent 7700kcals with a pretty amazing degree of correlation (even although 7700 kcals is a very notional value).

Suppose that you ate 125 kcals more than your body needed every day for a year.  That’s not a great amount over the 2400 kcal daily allowance for the average man or 2000 kcals for the average woman, yet those additional calories, from a simple energy balance standpoint, would produce 5.9kg of fat storage per year if they were not needed.  What food could you eat for 125kcals?  If the food was celery, then quite a lot – about 1.25kg!  On the other hand if you went for highly refined sugary carbohydrates and opted for a single Twix chocolate biscuit (i.e. half of a normal twin pack) then that’s your entire 125 kcals gone (and probably pretty quickly too!).  So just eating a single additional chocolate biscuit every day for a year above what your body actually needs could lead to almost 6kg of fat storage!

While the prospect of a single Twix biscuit every day leading to a weight gain of 6 kg in one year may be very depressing, there is an upside to the scenario for if you reduce your calorie intake by the same amount then you can lose 6kg in a year.  That sounds much better doesn’t it?

When you are planning to lose weight the starting point is your weight loss target and the number of days over which you want to lose that weight.  Then you can estimate the required daily calorie restriction as follows :

Daily calorie restriction = (Weight loss target (kg) x 7700)/number of days

This equation shows that reducing our calorie intake by 550 kcals/day should allow a maximum weight loss of 0.5kg per week.  I found that it took a couple of weeks of dieting for the body to settle into regular fat burning mode but thereafter the weight loss was very predictable.

The calorie restriction can be achieved through a combination of reduced food consumption or increased exercise but, as explained below in the section “Calorie restriction vs exercise for weight loss” it is best to aim for a combination of food reduction and exercise, since the latter helps boost the metabolic rate for a period that extends beyond the actual exercise time.   I achieved about two thirds of my net calorie restriction through reduced food intake and one third from cardio and strength training exercises.   In addition I shifted the balance of my food intake to eliminate all sugars and simple carbohydrates, while eating more fat and protein.

The general medical advice on weight loss seems to be that very rapid weight loss is not a good idea, and that 1-2 lbs (~0.5-1kg) per week is a sensible target, although you should discuss specific goals with your doctor before embarking on any significant dietary change or weight loss programme.    In addition, rapid weight loss might actually increase the efficiency of your fat storage post-diet because of the effects of a hormone called ghrelin which stimulates feelings of hunger.   Ghrelin has been associated with "yo-yo" dieting whereby weight loss is rapidly regained after returning to a "normal" diet.   In my case however the pattern of eating has changed permanently to the Mediterranean style so there has been no change in food type at the end of my weight loss period.  I just eat more calories to maintain my weight which has remained constant now for two months following the weight  loss.   Had I returned to eating sugar and simple carbohydrates then I am quite sure that my weight would have started to increase.

3.7   My food intake and weight loss figures over six months

Over the six month exercise my weight reduced from 85.5kg to 68kg and my fat level from 29.5% to 8.3%.   I diligently tracked everything I ate, as well as calories spent in exercise sessions in the gym, which meant that I was able to check how accurately the energy balance equation applied.  In my case genes, microbes, and other factors seemed to play no major role in distorting the energy balance equation which all added add up very accurately.

So here are the specific numbers for my diet.  On my two Fast days I ate 600 kcals per day.  On my Feast days I had no particular calorie target beyond aiming to reduce my calorie intake a little from the calculated TDEE requirement of 2367 kcals per day.  Over approximately  six months, I averaged 2000 kcals per day on the Feast days so my total weekly intake was 5x2000 + 2x600 = 11200 kcals which gives an overall daily average of 1600 kcals, equivalent to  an average daily restriction of 2367-1600 kcals which = 767 kcals per day.

Cutting out about 400 kcals on Feast days day is really easy to do and, in combination with the big reduction on the two Fast days, this meant that I was restricting calories by about 5369 kcals per week (=7x767) or the fat equivalent of 5639/7700 kg, or 0.7 kg of fat.  In addition I had cardio, high intensity and resistance training sessions which, averaged over the six months, came to 2500 kcals per week or the equivalent of 2500/7700 kg, or 0.3 kg of fat.  This all turned into predictable and repeatable weight loss too, for after the first couple of weeks of erratic loss the body settled down to almost exactly 1kg of weight loss per week.  I also was amazed to see that if I treated the gym exercise as one off calorie requirements to be accounted for as additional calorie intake, then my normal daily calorie requirements turned out to be 2360 kcals per day which correlates unbelievably well with the TDEE figure of 2367 kcals/day calculated at the start of the exercise.

The energy balance relationship did start to break down towards the end of the six months as my gym sessions had increased my fitness and aerobic capacity, and I had added significant muscle mass.   At that point weight loss per se became meaningless because adding muscle mass was a desirable thing. The body fat calipers showed I was still losing fat but I was also adding denser muscle, so my body volume continued to decrease gradually while my weight increased (and my BMI degraded of course!).

[Note :  You can’t turn fat into muscle.  There are no belly exercises to lose belly fat because the body controls how and where fat is deposited and lost.  You need to perform cardio exercise to lose fat then perform specific weight or resistance training to add muscle mass where you want it to develop].

The numbers above show that while the Calories in = Calories out energy balance may be an over simplification it does provide a simple way to initially plan how much fat you want to lose and how many calories you therefore need to restrict.  The online TDEE calculator referred to in section 3.4 seemed to calculate a daily calorie requirement that was very accurate for me so I would recommend you start with that.   Alternatively if you just assumed a need for 2400 kcals per day for a man and 2000 kcals per day for woman then you probably would not be far out.

If you lose weight too quickly or slowly after the first couple of weeks then it is easy to adjust the daily calorie allowance up or down.  You do not need to fixate on a particular calorie intake on Feast Days as long as your overall average is sufficiently less than your average daily needs.  So you can eat a bit more one day and cut back on the next.  However, you will definitely need to track your calorie consumption fairly accurately if you want to stay in control.  Weighing yourself regularly is important but day to day weight variations are normal as you eat, digest, and even shower so you cannot take day to day variations as an accurate indicator of weight loss or gain.  However if you weigh yourself daily (at the same time, e.g. in the morning before food or showering) and then average those weights over a period of 7-10 days you will begin to see an accurate trend.

At the time of writing my weekly gym sessions have increased to about 5500 kcals/week and I am doing much more resistance training to increase muscle mass.   I still fast for two days each week in order to maintain the health benefits for cholesterol, blood sugar and the IGF1 growth hormone levels but I have increased calories on the Feast days to ensure that my weight remains stable.  I have slightly relaxed the Fast day calorie limit and will now eat up to 800 kcals, although I still ensure a full 24 hour fasting period by only eating one meal on Fast days.