It may not be necessary to go hungry – intermittent fasting does not cause weight loss anyway
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Intermittent fasting does not appear to be more effective for weight loss than doing nothing at all, according to a review of studies involving people who were overweight or obese.
The diet has become a popular weight loss strategy in recent years and involves alternating between periods of fasting and normal eating. This can include eating only during a specific window each day, such as the 16:8 diet, where you fast for 16 hours and eat within an 8-hour period; or eat normally some days and very little others, like the 5:2 diet, where you eat normally five days a week and restrict calories on the other two.
The idea is that restricting when people can eat reduces their total caloric intake, but a randomized controlled trial found that it’s no better for weight loss than counting calories.
To learn more, Luis Garegnani of the Italian Hospital in Buenos Aires, Argentina, and his colleagues analyzed data from 22 randomized controlled trials of intermittent fasting, involving nearly 2,000 adults across North America, Europe, China, Australia and South America. The participants were aged 18 to 80 and were either overweight or obese.
First, they compared intermittent fasting with traditional dietary advice and found that there is probably no significant difference in terms of weight loss. Then they compared intermittent fasting to doing nothing at all and found that neither leads to more weight loss. “Intermittent fasting just doesn’t seem to work for overweight or obese adults trying to lose weight,” Garegnani said in a news release.
However, inconsistencies across trials make it challenging to draw firm conclusions, he says. Still, when the researchers grouped the results by gender or type of intermittent fasting, they found that the approach still didn’t seem to help with weight loss.
But Satchidananda Panda of the Salk Institute for Biological Studies in California notes that most of the studies in the review did not measure adherence to intermittent fasting. “If we don’t know whether the participants actually followed the intervention, what exactly are we reviewing systematically?” he says. “It’s a bit like building a cathedral on quicksand and then performing a meta-analysis of the architecture.”
The analysis focused on weight loss, so it is also not clear whether intermittent fasting has other health effects, good or bad. For example, some studies suggest that it may increase the risk of heart disease, while others indicate that it boosts immunity and improves gut and liver function.
“Intermittent fasting is not a miracle solution,” says Garegnani. “(It) may be a useful option for some individuals, but it should not distract from broader population-level strategies to prevent and manage obesity.”
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