Low-fat diet has limited success in improving female body composition
MedWire News: Women who follow a low-fat diet exhibit modest but significant reductions in body fat, fat mass, and lean mass after 1 year, US researchers report.
Most changes were not sustained over the longer-term, however, and the magnitude of response varied among subgroups, highlighting the need for more personalized approaches to dietary modification.
The findings come from a new analysis of the Dietary Modification Trial of the Women's Health Initiative study. This was a randomized controlled trial in which 48,835 postmenopausal women aged 50-79 years followed either a low-fat ( ≤ l 20% of total energy) or a usual diet.
All women underwent whole-body dual-energy X-ray absorptiometry scans at baseline and during follow-up.
Over the whole follow-up, the intervention was associated with small but significant reductions of 0.8% in body fat, 1.1 kg in fat mass, and 0.17 kg in lean mass.
Between baseline and year 3, women in the intervention group lost percentage body fat, whereas women in the comparison group gained percentage body fat; the difference between the groups was modest (<1%) but statistically significant.
By year 6, however, mean percentage body fat had increased from baseline in both groups. Although women in the intervention group gained slightly less, their change from baseline was no longer significantly different versus control women.
A similar pattern was observed for lean mass, with the between-group differences being significant at years 1 and 3, but not at year 6.
By contrast, the change in fat mass was significantly greater in the diet group than in controls at years 1, 3, and 6.
The impact of a low-fat diet on body composition also varied among subgroups, being more pronounced in White versus Black or Hispanic women, and in normal-weight versus overweight women.
"Promotion of small changes in diet and exercise, decreases in body fat, or even prevention of weight gain have been discussed as important public health strategies for combating the obesity epidemic," write Cara Carty (Fred Hutchinson Cancer Research Center, Seattle, Washington) in the American Journal of Clinical Nutrition.
"Our analysis is particularly informative on this standpoint; we describe an intervention that was significantly associated with these key outcomes (decreases in percentage body fat and fat mass) in an ethnically diverse population of US postmenopausal women."
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By Joanna Lyford