Low-fat dietary pattern and weight change over 7 years: the Women's Health Initiative Dietary Modification Trial.
BACKGROUND
Obesity in the United States has increased dramatically during the past several decades. There is debate about optimum calorie balance for prevention of weight gain, and proponents of some low-carbohydrate diet regimens have suggested that the increasing obesity may be attributed, in part, to low-fat, high-carbohydrate diets.


OBJECTIVE
To report data on body weight in a long-term, low-fat diet trial for which the primary end points were breast and colorectal cancer and to examine the relationships between weight changes and changes in dietary components.


METHODS
Randomized intervention trial of 48,835 postmenopausal women in the United States who were of diverse backgrounds and ethnicities and participated in the Women's Health Initiative Dietary Modification Trial; 40% (19,541) were randomized to the intervention and 60% (29,294) to a control group. Study enrollment was between 1993 and 1998, and this analysis includes a mean follow-up of 7.5 years (through August 31, 2004).


METHODS
The intervention included group and individual sessions to promote a decrease in fat intake and increases in vegetable, fruit, and grain consumption and did not include weight loss or caloric restriction goals. The control group received diet-related education materials.


METHODS
Change in body weight from baseline to follow-up.


RESULTS
Women in the intervention group lost weight in the first year (mean of 2.2 kg, P<.001) and maintained lower weight than control women during an average 7.5 years of follow-up (difference, 1.9 kg, P<.001 at 1 year and 0.4 kg, P = .01 at 7.5 years). No tendency toward weight gain was observed in intervention group women overall or when stratified by age, ethnicity, or body mass index. Weight loss was greatest among women in either group who decreased their percentage of energy from fat. A similar but lesser trend was observed with increases in vegetable and fruit servings, and a nonsignificant trend toward weight loss occurred with increasing intake of fiber.


CONCLUSIONS
A low-fat eating pattern does not result in weight gain in postmenopausal women. Clinical Trial Registration ClinicalTrials.gov, NCT00000611.
Howard
Barbara V
BV
MedStar Research Institute, Washington, DC, USA. Barbara.V.Howard@MedStar.net
Manson
JoAnn E
JE
Stefanick
Marcia L
ML
Beresford
Shirley A
SA
Frank
Gail
G
Jones
Bobette
B
Rodabough
Rebecca J
RJ
Snetselaar
Linda
L
Thomson
Cynthia
C
Tinker
Lesley
L
Vitolins
Mara
M
Prentice
Ross
R
D000368:Aged; D000886:Anthropometry; D015930:Diet Records; D018752:Diet, Fat-Restricted; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D017698:Postmenopause; D015431:Weight Loss