Overweight people do not convert more carbohydrates to fat than lean people

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Wednesday, August 11, 2004 9:40 am Email this article
Overweight people do not convert more carbohydrates to fat than lean people even when overfeed with carbohydrates according to a new study from Switzerland. Subjects: 11 lean, 8 overweight

The study included five lean males and six lean females with an average body mass index (BMI) of 21, and four overweight males and four overweight females with an average BMI of 30.

Two occassions: One normal calorie diet, second high-calorie/high-carbohydrate diet

They were studied on two occassions.

On one occasion, they ate a normal-calorie diet containing 50 percent of calories as carbohydrates for four days and then were tested. This is a normal amount of carbohydrates for most people.

On the second occasion, they received a a high-calorie diet diet containing 75 percent more calories than they normal ate, containing 71 percent of calories as carbohydrates. This would provide about two-and-half times as many carbohydrates as a person would normally eat.

Tested carbohydrate-to-fat conversion following sugar ingestion

After each four day period, they were given a large dose of glucose (sugar) and were tested to see how much of the sugar was converted to fat over the next five hours. The process is known as de novo lipogenesis.

After the high-calorie/high-carbohydrate period, both the lean group and the overweight group converted more of the sugar into fat, however, the increase was much greater in the lean group than the overweight group.

Lean people convert 2.4 times more carbohydrate-to-fat than overweight people

The amount of fat made from carbohydrates was 2.4 times greater in the lean group than the overweight group.

Conclusion

“Carbohydrate overfeeding does not stimulate [the conversion of carbohydates to fat] to a larger extent in overweight than lean subjects,” the paper concludes.

Comment: Conversion of carbohydrates to fat is not a significant cause of overweight

This suggests to me that the conversion of carbohydrates to fat is not a major cause of people being overweight or staying overweight.

Carbohydrate researcher Jean-Pierre Flatt agrees

In an enlightening interview, carbohydrate research Jean-Pierre Flatt, Ph.D. noted that carbohydrates are not easily converted to fat. When asked if most bodyfat comes from carbohydrates, as was claimed by the physician-authors of the book The Sugar Busters, Flatt replied, “No, absolutely not. That is complete nonsense.”

REFERENCE

Minehira K, Vega N, Vidal H, Acheson K, Tappy L. Effect of carbohydrate overfeeding on whole body macronutrient metabolism and expression of lipogenic enzymes in adipose tissue of lean and overweight humans. Int J Obes Relat Metab Disord. 2004 Aug 10.

AUTHOR’S CONTACT INFORMATION

K. Minehira
Department of Physiology
University of Lausanne
Lausanne, Switzerland

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