Diets Make You Fat
If you want to lose weight, you have to diet and exercise more. Or so goes the guidance pedalled by doctors, government, NHS, diet and weight loss companies and the media.
The problem is that it doesn't work. First, you will almost certainly fail to reach your target weight, and second, you are pretty well guaranteed to weigh more than when you started less than a year later.
Scientists have known this for a long time. Initially, they didn't understand why, but they identified some of the mechanisms about 20 years ago, and there has been a comprehensive understanding for at least five years.1
Weak-willed or greedy?
Many people blame themselves for failing to stick to their diet or maintain their reduced weight, concluding that they lack will power or are simply greedy. Alternatively, people seek to blame something else - slow metabolism or genes being the two most common.
If your doctor advises you to embark on a diet for medical reasons, you are likely to be labelled as "non-compliant" if you fail to stick to your diet. This has all sorts of consequences for your future relationship with your GP practice.
Nothing to do with will-power
What is really happening is your body is responding to the threat it perceives it is facing; a food shortage.
We have sophisticated systems designed to ensure survival and procreation. They are very powerful and generally very effective; if we don't mess them up.
So when you go on a diet, the body thinks it's facing a famine and tries to increase its energy reserves. It kicks off a series of changes; raises your cortisol levels (the stress hormone), encourages you to conserve energy reducing the amount of energy expended on non-essential activity. It will make you more sluggish, reduce your libido, make your body and mind more depressed and can actually produce clinical depression and anxiety if carried too far.
The two things it is guaranteed to do are make you fixate on food and reduce the amount of passive energy2 you expend.