It’s December 2018.  You went on a couple of diets and now in December you’re 10kg heavier than the start of Jan.  You’re looking forward to Jan 2019 so you can start another diet.  But how successfully will you be?  There is a problem with dieting and that is biology is against us (or for us as we shall see).  Science has discovered that dieting doesn’t work and it’s because of biology and we will see how biology affects weight gain in dieters.

Statistics of Weight Gain

Statistics show that the long term rate of weight gain after diet is high.  In scientific studies it has been shown in the US, individuals that have tried to lose weight, only 20% of them have been able to achieve and maintain a 10% reduction in body weight over a year.  One third of people who lost weight regained the weight in the first year and the majority of people regained their weight in three to five years after first having lost weight.  As a recovering dieter, these statistics are shocking.  The latest research shows that it is the strong influence of biology that stops us from losing weight and makes us stack on the weight after we stopped dieting.

Three Forces That Are Keeping Our Weight Stable

There are three forces that control our weight.  These are the environment, our behaviour and biology that wants to keep our weight stable.  But underpinning all of these are our genetics.  Our biology, in the face of changes in these forces keeps us from perpetual weight gain or wasting away, always tries to lead the body to a homeostatic weight or a ‘set point’.  It leads us to eat more when we don’t eat enough food or eat less food when we are eating too much but this gets muddled when we diet.

Hormones That Are Effecting Our Appetite

Two hormones that are responsible for sending signals to the brain that let the brain know when to eat are leptin (secreted by fat cells) and insulin (secreted by the pancreas).  During an energy restricted diet and weight loss, the adipose tissue (fat cells) reduce in size (you don’t lose fat cells during weight loss they just get smaller).  This decreases the level of Leptin and Insulin in the blood stream sending a signal to the brain that there isn’t enough energy.  The brain then releases hormones to the body to increase appetite signalling the body to eat more food for weight gain.  The signalling goes to the hypothalamus, the centre where all our hunger and satiety cues come from. 

During dieting there is a reduced sensitivity to satiety signals meaning that the person will increase meal size with higher food intake.  This means that when you are dieting you get very hungry and want to eat and will have a tendency to overeat (why eat a piece of cake when you can eat the whole cake). 

What Happens To Long Term Dieters?

But the kicker is what happens in the long term from long term dieting.  Weight loss causes a reduction in energy expenditure, or our metabolic rate reduces.  But this continues after the weight has been regained along with the  increased appetite.  What’s worse is that the energy gap between how much energy the body burns and the increase in appetite increases the longer the person is on the diet and doesn’t dissipate on weight maintenance.  This means that your metabolism continues to slow and your appetite continues to increase the longer you’re on a diet and remains at that level even after you’ve stopped dieting and a new ‘set point’ (homeostatic weight) is achieved (ie you’ve now stacked on 10kg)

In Summary

In earlier blogs we’ve talked about what restrictive dieting can do to the brain (see blog) – it increases dopamine receptiveness so that we over eat.  And here is another example of biology stopping us from dieting.  In this example we have shown that the body wants to maintain homeostasis (a ‘set point’) and will do everything it can do to get us there.  What’s the solution? Stop dieting as the body knows how much to eat and adopt an intuitive way of eating.  This proven concept uses our hunger and satiety cues to listen to what the body needs in order to stay in homeostasis.  A good book to read on this is ‘Just Eat It’ by Laura Thomas.


Paul S. MacLean, Audrey Bergouignan, Marc-Andre Cornier, and Matthew R. Jackman, ‘Biology’s response to dieting: the impetus for weight regain’, Am J Physiol Regul Integr Comp Physiol. 2011 Sep; 301(3): R581–R600.






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