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The incidence of obesity is increasing in America at a disturbing rate, and it is having a particularly devastating impact on women. Since 1980, obesity in both men and women has increased by over 50%, and currently over half of all Americans are overweight or obese.
While roughly 9% more men than women between the ages of 20 and 80 have a BMI of 25 or greater, more women than men are seriously overweight, qualifying as obese, with BMIs of 30 or greater.
Twenty-five percent of US women and 19.5% of men are obese, with higher percentages for minority women (36.7% among non-Hispanic African-American women, and 33.3% among Mexican American women). Sixty percent of African American women aged 45 to 65 are either overweight or obese.
It is estimated that 33% to 40% of American women are trying to lose weight at any given time, as well as 20% to 24% of men. Given these alarming rates, and the profound health consequences of obesity, we as primary care practitioners have a responsibility to educate, motivate, and offer clinical guidance and management for our patients trying to lose weight and regain their health.
The reality is, though, there are no quick fixes. Obesity is very complex—metabolically and psychologically. Long-term, lasting weight loss takes long and hard work from both patients and practitioners. Here are just a few things that have appeared in the research recently that may offer some direction.
Weight Loss Diets: The A to Z Study
The A to Z weight loss study randomized 311 overweight women aged 25–50, to one of four controversial diets: the very low carbohydrate Atkins diet, the low-carb Zone diet, the low-fat, high-carb LEARN diet that also focused on lifestyle, exercise, attitudes, relationships and nutrition, and the very high-carb Ornish diet. Women in each group attended once weekly nutrition classes for 8 weeks and received a diet book outlining the particular diet to which they were assigned. Patients were assessed at 2, 6 and 12 months; evaluation included dietary intake and physical activity records, and anthropometric and metabolic measures.
Women lost a mean of 4.7 kg on Atkins, 2.6 kg on Ornish, 2.2 kg on LEARN and 1.6 kg on Zone. There was no significant difference between any of the groups in terms of body fat percentage and waist-hip ratios at one year, although the greatest decrease was in the Atkins group.
HDL cholesterol increases and triglyceride decreases were significantly better in the Atkins group compared with the other three diets. The Atkins dieters also had the greatest decrease in systolic and diastolic blood pressures of 7.6/4.4 mm Hg (Gardner C, et al. JAMA. 2007 Mar 7; 297: 969–977).
The A to Z study shows clearly that it is possible to lose weight by adherence to any of the 4 diets studied. However, patients and practitioners need to have realistic expectations: a 5 kg or roughly10 lb weight loss in one year, which was the best achieved weight-loss in this trial, is not a huge amount of weight to lose, especially for obese women.
That said, it is certainly meaningful and important, especially for women in the perimenopausal age zone. This is a time when most women typically gain weight. Holding steady, or losing 10 pounds is metabolically significant with probably long-term health benefits. Bear in mind that it is difficult to achieve compliance with any highly restrictive diet for one year.
Conjugated Linoleic Acid and Weight Loss
A recent double-blind controlled trial examined the impact of conjugated linoleic acid (CLA) in 118 overweight subjects with BMIs of 28–32 kg/m2. Study subjects were mostly women, and were given 3.4 g/day of CLA or placebo for 6 months. Measurements included total body weight, body fat mass (BFM), and waist size.
Those who took CLA lost 3.4% BFM and those in the placebo group lost 0.1%. In those subjects who had good compliance, there was a loss of 5.6% BFM. In women who were obese at the outset (BMI > 30 kg/m2), most fat loss was from the legs. In the treatment group, waist size decreased by more than one inch, or 2.7%. Women in the placebo group showed no change (Gaullier J, et al. Br J Nutr. 2007; 97: 550–560).
These data are not surprising given several previous reports showing that CLA reduces body weight. The primary mechanism behind the CLA effect is not spelled out, but it may be attributable to a reduction in the accumulation of fatty acids in fat cells via inhibition of lipoprotein lipase and promotion of carnitine palmitoyltransferase.
From an overall disease risk perspective, decreasing fat in the legs probably doesn’t have too much impact, but reduction in waist size certainly does. Abdominal weight gain and abdominal fat are both highly associated with an increased risk of cardiovascular disease. In other studies in which CLA was used for one to two years, investigators have seen declines in BFM as great as 9%. CLA is clearly an ally in helping women lose weight and reduce the burden of obesity-associated disease.
Calcium and Weight Loss
A sub-study of the Vitamins and Lifestyle (VITAL) study, focused on the effect of dietary calcium and supplemental calcium on 10-year weight change in 5,250 men and 5,341 women. All were aged 53–57 years, and completed questionnaires about supplement use for the previous 10 years, and dietary calcium intake for the preceding year. Data on height, current and previous weights, exercise, smoking history and demographic characteristics were also gathered.
Most individuals in the study were Caucasian, well-educated, and mostly non-smokers (except for 8% of them). The women had an average dietary calcium intake of 811 mg/day in the previous year, and the average combined dietary and supplemental calcium intake was an average of 1,094 mg/day.
Those women who took 500 mg or more of supplemental calcium either during the study or during the previous 10 years, showed significantly less weight gain over those 10 years compared to the women who did not take supplemental calcium. The difference was about 4 lbs. Dietary calcium alone was not associated with lower weight gain. Calcium intake in men had no effect on weight gain (Gonzalez A, et al. J Am Diet Assoc. 2006 Jul; 106: 1066–1073).
Previous research has shown an inverse relationship between calcium intake and weight gain. The Gonzalez study seems to support that observation. However, interpretation of this study is limited because it relies exclusively on self-reported body weight, calcium intake and supplemental calcium over 10 years. The accuracy of self-reports is always questionable.
I cannot feel confident that this study alone provides adequate evidence to recommend either calcium supplements or dairy products to middle aged women in order to lose weight, or at least not gain weight. On the other hand, there are other compelling reasons for women to increase calcium and vitamin D intake as they age. Perhaps they will also receive a small benefit of less weight gain in addition to the other calcium/vitamin D–associated health benefits.
