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The Glycemic Index and Weight Loss

A high-GI diet is not tied to bigger bellies.

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Meter showing the glycemic index

It was a bit of a glycemic index research surprise: “There is scant scientific evidence that low-GI diets are superior to high-GI diets for weight loss and obesity prevention.” This is the somewhat unforeseen concluding statement from a team of American researchers.

The team reviewed 35 studies on more than 2 million people and found no differences in body mass index between those with high- versus low-glycemic index diets. A few of the studies in the analysis actually found people with a higher GI diet had a lower BMI.

The study—in Advances in Nutrition—also showed that a diet with more high-glycemic foods, otherwise known as “fast carbs,” do not generally lead to more weight loss or higher body fat compared to a lower-glycemic diet with more “slow carbs.”

The glycemic index was introduced in the early 80s as a way to classify foods according to their effects on blood sugar levels. While there are likely several other health benefits to choosing lower GI foods like vegetables and whole grains over higher GI ones such as white bread and sugary drinks, this can be a reminder that bodyweight is a very complex issue involving an array of modifying factors.

See also: Carbs and Type 2 Diabetes


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Matthew Kadey, MS, RD

Matthew Kadey, MS, RD, is a James Beard Award–winning food journalist, dietitian and author of the cookbook Rocket Fuel: Power-Packed Food for Sport + Adventure (VeloPress 2016). He has written for dozens of magazines, including Runner’s World, Men’s Health, Shape, Men’s Fitness and Muscle and Fitness.

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