Yo-yo effect not bigger after crash diet

Overweight people who lose a lot a weight in a short amount of time are no more likely to gain weight after dieting than people who lose weight more slowly. These were the results of a study conducted by Roel Vink, Edwin Mariman, Marleen Baak and others from Maastricht University, which was published this week in the journal Obesity. It was long assumed that crash dieting (losing weight in a short amount of time) was unhealthy, as it increases the likelihood of weight gain after the diet (yo-yo effect). This study, however, disproves that assumption, which can affect the dietary advice given to people who are overweight or obese.

In this study, sixty overweight and obese participants were divided into two groups. One group followed a very-low-calorie diet of 500 kilocalories per day over the course of five weeks. The other group followed a low-calorie diet of 1250 kilocalories per day over the course of twelve weeks. The participants in both groups lost an average of eight to nine kilos, which is roughly 10% of their body weight. All dietary advice was stopped after their diets ended. The participants were asked to return nine months later for a weigh-in. Both groups gained the same amount of weight: approximately 50% of the weight they lost during the diet. The five-week crash diet did not lead to more weight gain than the slower twelve-week diet. 'A yo-yo effect is not more likely after a crash diet than a more gradual diet,' says PhD candidate and researcher Roel Vink.

Two factors did influence post-diet weight gain: the amount of exercise after the diet and the amount of lean body mass lost during the diet. 'We think it involves a loss of muscle mass because the diets are low in calories and protein,' says Vink. “Participants who lost more muscle mass during the diet and those with a lower level of physical activity after the diet gained more weight. These factors likely lower energy metabolism, which could lead to weight gain when you resume a ‘normal’ diet,” according to the researchers. Additional research is being carried out to determine whether crash dieting can lead to other adverse effects and which factors contribute to weight gain after dieting.

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