Harvard Health Letter

In Brief: Low-carb dieting: Slimmer but sadder?

In Brief

Low-carb dieting: Slimmer but sadder?

Low-carb diets have done well in some head-to-head comparisons with other diets. And no matter what the diet, shedding a few pounds usually makes people happy.

But there's some research suggesting that Atkins-like diets (low in carbs, high in fat and protein) could make people's moods a little darker even if their bodies end up a little lighter. Carbohydrates promote the synthesis of serotonin, a neurotransmitter that seems to play a significant role in mood control. Some evidence suggests that avoiding carbs — and gorging on fat and protein instead — could reduce serotonin concentrations, giving some folks a case of the low-carb blues. And when diets have been tested for a short time (three weeks) in physically active people without a weight problem, low-carb eating has led to more fatigue and bad moods than high-carb eating.

Of course, those aren't the kind of people who typically set out to lose weight. So Australian researchers set out to see what sort of influence the diets would have on mood in people more inclined to do so. Their study randomly assigned 93 people who were overweight or obese (an average body mass index of 33.6) to either a low- or high-carb eating plan.

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