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Low carb diets may improve success of obesity treatment, finds study

Low carb diets may improve the success of obesity treatment by helping patients maintain weight loss, a study has suggested.

The research, carried out in the US, suggests that low carb diets lead to increased energy expenditure and reductions in levels of the hormone that causes hunger.

The study included 164 patients with initial BMIs of over 25 who managed to lose 12% of their body weight on an initial weight loss diet. After the initial 10-week weight loss period, the patients were assigned to either a high, moderate or low carb diet for a further 20 weeks.

The researchers found that patients on a low carb diet expended, on average, just over 200kcal per day more than those on high carb diets. They also had around a 12% reduction in levels of ghrelin, the hormone that causes hunger, compared to 5% in those on high carb diets.

Energy expenditure was more pronounced in patients who had the highest insulin concentrations before they started losing weight, with patients on low carb diets burning just over 300 kcal per day more than those on high carb diets.

The researchers say that the results are consistent with the carbohydrate-insulin model of obesity, where increased insulin levels after a high carbohydrate meal causes metabolic fuels to be stored as adipose tissue, a physiological state that may increase hunger and lead to lower energy expenditure.

They said in the paper: ‘Consistent with the carbohydrate-insulin model, lowering dietary carbohydrate increased energy expenditure during weight loss maintenance. This metabolic effect may improve the success of obesity treatment, especially among those with high insulin secretion.’

The research comes as the British Dietetic Association released a policy statement on their position regarding low carb diets in type 2 diabetics.

Duane Mellor, diabetes specialist and one of the authors of the policy statement, said: 'Low-carbohydrate diets have been an option for patients with type 2 diabetes for many years, and were included in Diabetes UK’s nutritional guidelines of type 2 diabetes in 2011 and again in 2018. For some people, these diets will be a way to successfully lose weight and improve their glycaemic control.

'However, it’s important to be clear that low-carbohydrate diets are not a sliver bullet. Not everyone finds it a suitable approach for them, and we know that other approaches have also been very effective in controlling and even reversing type 2 diabetes. Some advocates have claimed everyone should eat a low-carbohydrate diet, but this fails to take into account the many different factors that influence a person’s preference for their way of eating including culture, income and what works best for them. This is further complicated by the fact that low carbohydrate diets are often poorly defined, and the amounts of carbohydrate included varies significantly.'

BMJ 2018; available online 14th November

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