Breakfast may alter fat burning during exercise

NEW YORK (Reuters Health) - A small group of healthy, but sedentary, women who began to exercise appeared to burn more fat after eating a high-fiber, low-glycemic index breakfast, the findings from a small study suggest.

A close-up of granola is seen in this undated handout photo. (REUTERS/Newscom)

If confirmed by larger studies, these findings could have important implications for weight management, report researchers from the University of Nottingham in the UK.

Dr. Emma J. Stevenson and colleagues assessed post-exercise fat oxidation among eight non-dieting, healthy women after eating either a low-glycemic index or a high-glycemic index breakfast.

Each breakfast provided equal amounts of carbohydrates, protein, and dietary fat, but the low-glycemic index breakfast contained 3.5 grams of fiber from “muesli and milk, yoghurt and canned peaches, and a small amount of apple juice,” Stevenson told Reuters Health.

By contrast, the high-glycemic index breakfast provided 1.5 grams of fiber from “cornflakes and milk, white bread and jam, and a carbonated glucose drink,” said Stevenson, who is currently affiliated with Northumbria University.

Previous research has shown increased exercise-induced fat, rather than carbohydrate oxidation, among athletes who eat low glycemic index foods, Stevenson’s team reports in The Journal of Nutrition.

In the current study, on two separate occasions each of the eight women, who were 24 years old, on average, ate one of the two breakfasts, and 3 hours later walked for 60 minutes.

During exercise, the women showed higher total fat and lower total carbohydrate oxidation levels after eating the low-glycemic breakfasts.

Stevenson and colleagues report total fat oxidation levels of 7.4 and 3.7 grams per hour during exercise after women ate the low- and high glycemic breakfasts, respectively. Comparable total carbohydrate oxidation levels were 42.5 and 51.6 grams per hour, respectively.

Moreover, after eating identical lunches, the women reported feeling more full on days when they also ate the low glycemic breakfast.

These preliminary findings suggest a high-fiber, low-glycemic index breakfast may increase fat oxidation and help satiation. Further research should investigate the potential long-term benefits of combining low glycemic breakfasts with later exercise, Stevenson and colleagues surmise.

SOURCE: The Journal of Nutrition, May 2009.