There’s a lot more to weight loss than just ‘calories in, calories out’. A physician explains

For decades, people have been told that their weight problems can be solved by math: Calories in, calories out. If weight were a simple math equation, more people would likely be the weight they desire. But it is much more complicated.

There are several theories as to why it is difficult to lose weight. Some focus on genetics and metabolism while others claim environmental and social factors are more important. But which of these theories is correct, if any? Are people destined to be the weight their genetics, metabolism or environment dictate?

I am a diabetologist and physician specialiding in obesity medicine. Understanding what’s known and uncertain about these theories can help you potentially overcome your own biology to change your weight.

Set point weight

The concept of set point weight has been around since the 1950s. It suggests that the body has a regulatory system that defends a predetermined level of adipose tissue – commonly called fat – it maintains by changing hunger cues and energy expenditure. That predetermined fat level is governed by genetics, physiology and environmental factors.

This idea is supported by observations that after weight loss, appetite is increased and energy expenditure decreased until weight is restored. In theory, this process prevents the body from starving, even with significant weight loss. One study found that hormones that...

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