I lost 20 kilograms a few years ago and I did not regain the lost weight. I was able to eat meat and fries and chocolate and pasta
and more. I was helped by a publication I found on the Internet which explained weight loss in a clear, scientific (and
humoristic) manner. John Walker explains it all at https://www.fourmilab.ch/hackdiet/ and he calls it the Hacker's Diet (if the
above link happens to be down search the Web for “Hacker's Diet”). It's not really a diet, no menus or recipes or food
exclusions or other foolish things, but a methodical explanation of how you can control how much food you should eat in order
to achieve the weight loss you want. You can (and should) still eat every type of food, just not as much as you perhaps would
like. For someone scientifically inclined this is wonderful as you can really follow your progress, apply feedback and fine-tune
your weight almost like you would control the loudness of music by adjusting a volume button. It does require pencil and
paper (or a PC) to keep track of how much energy you are ingesting and to calculate your mean weight. It does also require
stepping on a weighing scale daily. The simple mathematical formulas and the feedback loop are explained at length in the
Hacker's Diet notes. I am not going to duplicate any of it here but I will give you a brief summary of how it worked for me.

If you eat the exact amount of food (energy) your current body size and activity level require you will not gain weight nor lose
weight. If you eat more you will put on weight. You can lose weight by temporarily ingesting less energy (calories) than your
body needs. There are thus basically two approaches to achieving weight loss:

- you can lose weight by ingesting less energy (calories) than you currently do (by eating less)
- you can lose weight by requiring more energy than you currently eat (by exercising more)

Obviously, a combination of both methods also works: you can lose weight by simultaneously exercising more and eating less.
Both approaches require commitment and perseverance, however. Losing weight by exercising requires spending an awful lot
of time exercising every day. For me it was easier to lose weight by controlling the amount of ingested calories (and exercise a
little bit).

Unfortunately food manufacturers and nutritionists still express energy in a non-standard unit called the calorie. The correct
internationally accepted unit for energy is the Joule but lots of people still use the antiquated calorie (or kilocalorie). In Europe
you can usually find both indicated on food packages, but not always, especially not on imported exotic food. One day the
calorie will become obsolete, but is is still in use today. Here is the ingested energy/body weight relationship expressed in both

1 kg body weight = 7700 kcal


1 kg body weight = 32200 kJ

In other words 1 kilogram of stored body fat corresponds roughly to 7700 kilocalories of energy (or 32200 kilojoules).
This is an approximation but it is good enough for losing or maintaining weight. If you forget the number here is a trick to
remember it: look at the small print on a pack of regular butter in your fridge, you will see that the energy content of butter is
roughly 750 kilocalories per 100g (7500 kilocalories per kilogram). That's very close to 7700 and that's no surprise: butter is an
emulsion containing mostly animal fat (we humans are animals too). So just remember 1 kilogram body weight corresponds to
roughly 7700 kilocalories. In other words if (over a certain period of time) you ingest 7700 kilocalories more than your body
burns, then the body will store the excess energy as 1 kilogram of excess (reserve) fat over that period of time. Another example:
Let's say you want to lose 3 kilograms of body weight over a period of 2 months then you need to ingest 7700 x 3 = 23100
kilocalories less than what your current energy intake is and do it during those 2 months (60 days). In other words you have to
reduce your food intake by 23100 / 60 or 385 kilocalories every day during two months. So, if you currently eat on average say
2200 kilocalories every day you should start eating 2200-385 = 1815 kilocalories during 2 months to achieve your weight loss
goal. These examples are given to illustrate how the equation works, they are not diets your need to follow. You need to do your
own calculations. Obviously, once you have reached your optimal weight, you should eat just enough calories for your new
size in order to maintain your optimal weight. This is easy to control using the feedback provided by your weighing scale.
Hacking my weight
Now, where do you start? Do you know how many kilocalories you really need today in order not to lose nor gain weight? The Hacker's Diet notes give you some hints as to what your energy needs may be depending on your current size and weight. You can use that as a starting point but you can also estimate you current needs yourself. Start a Hackers Diet for a month then reverse-engineer you calorie needs. For example if you have reduced your intake and eaten 1700 kilocalories every day for 30 days and after those 30 days you lost 1.2 kg then you lost an average of 1200 grams/30 or 40 grams per day. We know that 1 gram corresponds to 7.7 kilocalories (because 1kg is 7700 kilocalories) therefore you had a daily deficit of 7.7 x 40 = 308 kilocalories. Therefore your current no gain/no loss energy need would be 1700 + 308 = 2008 kilocalories per day. It's as simple as that!

For simple weight loss the above is all you need to understand. To maintain your new weight all you need to do is eat the amount of calories your body requires, not more, not less. If you want to go into finer details you will have to take into account that the less you weigh the less energy your body actually needs. That's easy to understand. For example, the less you weigh the less energy it takes to walk or go up the stairs. I re-calculated my no-gain/no-loss energy needs about every month. I used a least squares method to calculate the slope of my weight curve. I'm not going to drag you into that. I know, I'm a nerd. I started dieting at 1500 kcal for a month (was tough) then increased it to 1700, 1900, 2100 and finally 2300 kcal. It took me 7-8 months to lose 20 kg. I used a spreadsheet to keep track of kilocalories eaten and of lost weight. I also used an Android application to keep track of my daily weight, it is called “Libra” and it is easy to use, it reminds you to step on the weighing scale every morning, it works very well and produces a nice chart of you weight loss.

Finally, and this is not mentioned often, your energy needs are very dependent on the outside temperature and it can make a very sizeable difference. You need to eat less during a hot summer than in the winter when it's cold outside. That's normal because in hot weather you need significantly less energy to bring your body temperature to 37°C.

If you need to lose some weight (or a lot of weight as I did), head to John Walker's web site and start reading his “Hacker's Diet” pages. You can even download a PDF version so you can read it while on the move. Your body needs proteins and fats and carbohydrates and fibres and vitamins and minerals. Eat everything: meat, bread, vegetables, fruit, cereals, fat but don't eat more than your body needs. By now you know how to calculate the amount of kilocalories you should be eating. Don't fall for commercial diets. Those that work are, in effect, camouflaged and expensive methods to make you ingest less calories without you noticing. Some diets may be imbalanced, these are outright dangerous. Eat healthy.

It worked for me but required willpower and perseverance. I'm not a nutritionist nor am I a doctor and you are the only one responsible for what you do to yourself. Good luck and bon appétit.

Melvyn Fishel

Libra weight curve