It’s the number one question in the health world that seems to tear us apart: is a low-calorie, low-carb, or low-fat diet the key to successful long-term weight loss?

Well, a new study published in the journal BMJ has finally settled the debate once and for all, showing that individuals who follow a low-carbohydrate diet burn between 209 and 278 more calories per day than those on a high-carbohydrate diet.

To conduct the study, researchers from Harvard University randomised overweight and obese people who had previously lost weight, to one of three diets: the first to a high-carb diet (60 per cent of their daily calorie intake from carbs), the second to a moderate-carb diet (40 per cent of their daily calorie intake from carbs), and the third a low-carb diet (20 per cent of their daily calorie intake from carbs). All the participants’ protein intake remained fixed at 20 per cent, and calories were adjusted to stabilize weight and stop further weight loss, making it more likely that any observed difference in calorie consumption was not from weight loss, but from the types of macros consumed.

After the 20-week long experiment, the researchers found those on the low-carb diet increased their resting expenditure by over 200 calories per day, while the high-carb group decreased their resting energy expenditure. This translated to 50 to 70 calories more per day for every 10 per cent decrease in carbohydrate intake.

“If this difference persists—and we saw no drop-off during the 20 weeks of our study—the effect would translate into about a 20-pound weight loss after three years, with no change in calorie intake,” said PhD and co-author of the study, Cara Ebbeling, in a press release.

David Ludwig, MD, and Ebbling’s co-author explained it comes down the insulin levels. Processed carbohydrates—which “flooded our diets during the low-fat era”—raise insulin levels, he said in the press release, which drives fat cells to store excess calories. This increases hunger and slows metabolism, which is “a recipe for weight gain.”

The study found those on the low-carb diet who had high levels of insulin secretion – which is produced after consuming glucose (the sugar found in carbs) – burned even more calories; up to 478 calories per day.

The study proves why the conventional model of ‘calories in, calories out’ is not the best path to weight loss. Instead, more effective and sustainable long-term weight loss comes down to the types of calories we consume.

For more like this, this is the exact time of the day you should eat carbs if you want to lose weight, and these are the surprising foods that have more carbs than a piece of bread.

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