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Obesity: an imbalance in calories in vs calories out… or is it something else?

If you have ever watched the London, Boston or Comrades marathons on TV, you will have noticed that 3 types of able-bodied runners take part in these gruelling events. Firstly, there are the skinny elite athletes then there are normal weight runners and finally some overweight participants pounding the pavement.

Now if a calorie was just a calorie then only seeing skinny and normal weight runners on our TV screens would be the rule. But overweight runners are there for all to see, despite them having probably trained just as hard as those in the skinny and normal weight groups. But how is it possible that the overweight marathon runners are still overweight after all their training if exercise is the answer to weight loss?

In 2008, the controversial science writer Gary Taubes published a seminal book on obesity and other aspects of the Metabolic Syndrome entitled: The Diet Delusion. Taubes writes and I quote, “Obesity is a disorder of excess fat accumulation, not overeating, and not sedentary behaviour” This is, of course, not what we have been told by most experts nor what society will have us believe. Taubes goes on to say, “ Consuming excess calories does not cause us to grow fatter, any more that it causes a child to grow taller”. Now think about the implication of this statement: Is it possible that overweight and obese people have to eat more? Maybe they have no choice? Taubes’s also makes the important point that “Expending more energy than we consume does not lead to long-term weight loss: it leads to hunger.”

And so if “obesity is a disorder of excess fat accumulation” and if “consuming excess calories does not cause us to grow fatter” and if “expending more energy that we consume does not lead to long-term weight loss”, then what’s the cause of the obesity pandemic and, importantly, what’s the solution? I listened to a lecture by Dr Jason Fung, a Canadian specialist physician, who had a real go at the prevailing theory that people are overweight or obese because they eat too much and don’t exercise enough – the traditional ‘calories in calories out’ theory. I too have argued in the past that this is not a theory that stands up to close inspection, if for no other reason than we all know of people who diet and exercise and don’t lose weight and, conversely, know of others who eat as much as they like, don’t exercise and yet don’t put on any weight. Granted “Calories in vs Calories out” may work in the short term but it just does not work in the long-term. Why, you may ask?

The calorie or energy theory does not hold in the long term because the advocates of this theory confuse proximate cause with ultimate cause, says Dr Fung. What do he mean? Well, using the analogy of an aircraft crash: the plane crashes because it can’t overcome the law of gravity – and this is the proximate cause of the accident. The accident investigators find that the aircraft was not properly maintained and as a result there was a failure of a key system. This was the ultimate cause of the accident. Applying proximate cause and ultimate cause thinking to obesity and the energy theory, we do find that people who are overweight or obese may eat too much and not exercise enough. In other words they may be in energy imbalance, i.e. they store more fat than they burn but this the proximate cause and not the ultimate cause of being obese. Something else – the ultimate cause – is responsible.

Now if something else other than “Calories in vs Calories out” is causing the energy imbalance, which manifests as weight gain, then it follows that simply correcting the energy imbalance by reducing calories in and increasing calories out can’t be the solution. And we know this because research shows that while most people who go on calorie restricted diets may lose a bit of weight in the short term, they soon plateau and eventually often regain the weight they initially lost. The energy balance theory does not work in the long-term principally because our metabolism eventually adapts to the ‘new normal’ of energy in and energy out by adjusting the body’s metabolic set-point – a sort of internal ‘fat thermostat’. According to set-point theory our weight is kept stable at a given set-point so that we can optimise bodily activity as well as maintain a stable and optimistic mood.

If the set-point drops too low, then we respond by becoming hungry and by reducing the amount of energy expended and this will continue until a new set-point is arrived at – in other words until energy balance or homeostasis is restored. Now eating less and exercising more does have some influence on the set-point –moving it up or down – but it’s influence is limited. The main drivers of the set-point are hormonal and the two main hormones at play appear to be insulin and cortisol. We know this because if we give people insulin and cortisone they gain weight and if we stop giving them these hormones they lose the weight they gained.

We don’t fully understand the mechanism by which insulin and cortisol cause weight gain but we do know what causes the body to over produce these hormones. In the case of insulin the major culprit is dietary carbohydrate which is turned into sugar in the body and it’s the sugar that causes the body to produce insulin. Too much insulin equals weight gain. Low or normal insulin equals weight loss. If high levels of insulin cause us to store fat and low levels of insulin help us to burn fat then the main cause of being overweight and obese is “…an imbalance – a disequilibrium – in the hormonal regulation of adipose tissue and fat metabolism”. In plain English: it’s too much insulin that makes us fat!

Chronic stress and sleep deprivation are associated with the overproduction of cortisol, which in turn is associated with weight gain. Get these hormones under control, especially insulin, with lifestyle modification and you are well on your way to losing weight and keeping it off.

In summary: The answer to being overweight and obese is mostly to be found in correcting the insulin imbalance. And that means eliminating or significantly reducing refined carbohydrate consumption. “The fewer carbohydrates we consume, the leaner we will be”… says Dr Fung and, I can add, the healthier we will be.

If you have any questions arising out of this podcast, please email me at

I am Dr Peter Hill from UpForIt. Till next time: stay healthy & safe.