Long-term weight loss - why diet alone may not work

Obesity: stats and facts‍

According to the latest available data, 67% of Australian adults are overweight or obese, which is about 12.5 million people nationwide.¹ This is a 10% increase from 1995 - and since overweight and obesity increases the chances of developing various chronic conditions, it is a cause for concern.¹‍

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A meta-analysis of 29 long-term weight loss studies found that over 50% of weight lost was regained within two years, jumping up to 80% by five years.² 

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Despite these facts, people still think of obesity as a lack of willpower, where people need to eat less and move more.³ However, this is not the case, as obesity is a complex, chronic condition involving a lot more factors than diet and exercise alone (though they do play an important role).³

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Why cutting calories isn’t enough‍

The simplest description of how obesity occurs is energy intake exceeding energy expenditure over a period of time.⁴ So it’s easy to see why the obvious solution is to reduce the amount of energy intake (calories). But the causes of obesity are far more complex and range from genetic, behavioural to environmental and psychological factors.³

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Let’s talk about diet‍

With all that said, diet does play an important role in weight management. The types of food you eat will impact your weight - for example the increase in access to processed foods with high levels of saturated fats, salt and sugar are known to contribute to weight gain - especially when coupled with low levels of physical activity.² So choosing what you eat is as important as how much. Try and make sure your diet is full of low-energy foods like vegetables and fruits, and not so much of high-energy, processed foods.^2,5 

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Reducing or restricting energy intake are also viable options for weight management - but they are not to be confused with ‘fad’ diets. A reduced energy diet is one where you increase the number of vegetables, fruit, wholegrains, legumes, nuts, seeds, lean meat, chicken, fish, eggs and dairy while reducing the number of “sometimes” foods (food with high energy, but low levels of nutrients like processed foods).³ A low energy diet is one where one or two meals are replaced with specially formulated meal replacements while a very low energy diet replaces more meals with replacements - these should only be done under the supervision of a healthcare professional.³

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The weight set-point theory‍

Research conducted on the physiological mechanisms of obesity and weight gain has shown that there could be a weight ‘set-point’ for each person. This is the weight that your body deems ‘normal’ and will try to maintain, by adjusting things like your appetite and metabolism.⁶ 

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In the environment we live in, consumption of highly processed foods and foods with high energy content (but low nutritional value) can block our bodies natural weight set-point.⁶ From an evolutionary view, our bodies are designed to protect against weight loss, not weight gain. So the systems that control weight gain can be easily overridden.⁷ 

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There are two systems that manage how your body maintains weight - the homeostatic system (the parts that control hunger and metabolism) and the hedonic system (the reward system). The homeostatic system includes the hypothalamus in the brain as well as hormones from the gut and fat cells which sense weight loss or gain and signal the body to either use more or less energy to maintain the weight set point.⁸ The homeostatic system can be influenced by your genetics and your environment to ‘adjust’ the weight set point so that your body thinks it’s ‘normal’ weight is higher than it used to be - this can make losing weight difficult as your body will try and bounce back to this new ‘normal’.⁸ 

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The hedonic system, sometimes referred to as hedonic eating, controls the desire for food and the pleasure that eating gives. By stimulating brain cells in this reward centre, foods that are high energy but low in nutrients become even more desirable, potentially leading to overeating.⁸ Hedonic eating can even modify the homeostatic system contributing to the shift in weight set point.⁸