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Date of release: 28 February, 2011

WHI Dietary Modification Trial – disappointing results?


Coincident with the December publication of data from the Women’s Health Initiative (WHI) Dietary Modification Trial [1], which failed to show decreased risk of breast cancer, colon cancer or coronary heart disease in a controlled trial of 48,835 postmenopausal women (50–79 years old) who lowered their fat intake by 7.8% and increased their carbohydrate intake by 7.6%, there appeared an additional study of a subset of the same group of women and data, this time examining whether the same dietary change had brought about any significant changes in fat mass, lean mass and/or percentage body fat, measured by DXA scans at 1 year, 3 years and 6 years of follow-up [2]. The intervention women experienced significantly greater reductions in percentage body fat, fat mass, and lean mass at years 1 and 3 than did women in the comparison group (all p < 0.05). At year 6, only the fat mass change was significantly different between groups. Overall, the intervention was associated with reductions in percentage body fat (-0.8%; 95% confidence interval (CI) -1.0%, -0.6%); fat mass (-1.1 kg; 95% CI -1.3, -0.8 kg), and lean mass (-0.17 kg; 95% CI -0.28, -0.06 kg) during follow-up (all p < 0.003). Intervention associations varied by race-ethnicity, body mass index, diabetes, and hormone therapy and remained significant after adjustment for physical activity. Only non-diabetic, white intervention subjects lost percentage of body fat, more fat mass and (in the case of non-hormone replacers) more lean mass at years 1 and 3, but by year 6 only the fat mass loss was greater in the intervention group. Women on hormone replacement did not lose lean mass; others did. The authors acknowledge that the observed loss of lean mass is not a desirable change. They emphasize that body mass index may fail to accurately show percentage body fat which can increase with age in persons not gaining weight. Compliance was assessed only on patient reporting.

Comment

Issues not covered sufficiently in the article include the following: unmeasured or unmeasurable patient compliance, possible nutritional deficits (cholesterol, fat-soluble vitamins, omega-3 fats), the fact that the first 5 pounds of weight loss are considered to be water, the miniscule amount of weight loss and body-composition changes achieved in the study and the cessation of such change after 1 or 3 years, the controversy as to whether cholesterol is the major cause of heart disease, the controversy as to whether increased carbohydrates in the diet increases chronic inflammation of the cardiovascular system, the possibility that some non-fat foods (such as gluten-containing foods) contribute substantially to disease, the deleterious effect on blood glucose of a diet higher in carbohydrates, the relative success of high-fat, low-carbohydrate diets for substantial and brisk weight loss in the obese and the relative lack of success of low-fat, high-carbohydrate diets for weight loss in the obese. If an obese patient is being put at increased risk of heart disease and cardiac death, she can lose the weight most comfortably (no hunger) and most quickly via a high-fat, low-carbohydrate (or no-carbohydrate) diet. The obese patients in this study lived for 6 years with no meaningful improvement in their health outlook. Apparently, the direction of this expensively tax-funded research is toward the design of strategies which will allow middle-aged, obese patients to be told their health is improved in spite of little or no weight loss. This pair of studies [1, 2] brings to mind a huge, expensive government study insisting that aging women were safer if gonadal hormone deficiency was the one hormonal deficiency they did not replace.

Comentario

Laura Fisher
Providence, Utah, USA

    References

  1. Howard BV, Curb JD, Eaton CB, et al. Low-fat dietary pattern and lipoprotein risk factors: the Womens Health Initiative Dietary Modification Trial. Am J Clin Nutr 2010;91:860-74.
    http://www.ncbi.nlm.nih.gov/pubmed/20164311

  2. Carty CL, Kooperberg C, Neuhouser ML, et al. Low-fat dietary pattern and change in body-composition traits in the Womens Health Initiative Dietary Modification Trial. Am J Clin Nutr 2010 Dec 22. Epub ahead of print.
    http://www.ncbi.nlm.nih.gov/pubmed/21177798