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Med J Aust 2000; 173 Suppl 6 November: S100-S101

Half of all women in Australia over 45 years of age are overweight (body mass index, greater than or equal to 25) or obese (body mass index, greater than or equal to 30). While it is recognised that body weight increases with parity, many women believe that weight gain also occurs with menopause. Prospective studies of body composition during menopause show increasing total and central abdominal fat and decreasing lean muscle tissue.^1,2 However, these changes in body composition can not be separated from the effects of the decrease in physical activity which commonly accompanies ageing. Individual women may find it difficult to differentiate the effect of age-progressive weight gain (common to both men and women) from a specific effect of oestrogen deficiency. Weight changes can often be quite marked in midlife, but weight gain has been found to be associated with age, not menopause.³

Fat mass and body shape in women of menopausal age

In middle-aged women, genetic factors remain the strongest influence on the amount and distribution of body fat, accounting for up to 60% of the variance.^4,5 Among the environmental factors leading to total and central obesity, decreased physical activity is more important than energy intake and dietary composition.⁶ Physical activity lowers the risk of type 2 diabetes in women at least partly through improved muscle insulin sensitivity, independent of body weight.⁷ It maintains lean muscle mass, so that aerobically fit older women do not, on average, have less muscle mass than younger women, and thus tend to have greater strength, aerobic capacity and resting energy expenditure than expected for age.⁸ In the largest study which directly measured energy expenditure in older women, there was a significant relationship between aerobic fitness and energy expenditure related to daily physical activity.⁹ These effects all contribute to the lower amounts of total and central body fat in menopausal women who are more physically active.

There is, however, substantial evidence that body fat redistributes to the abdominal region during and after the menopause, which may be attributed to the effects of oestrogen deficiency on adipocyte metabolism and fat partitioning.¹⁰ In cross-sectional twin studies, hormone replacement therapy was associated with less central (but not total) body fat, while smoking was associated with both less total and central body fat.¹¹ A prospective controlled study of oestrogen replacement therapy supports the role of oestrogen in preventing the increase in central fat deposition with menopause.¹²

Risks of increased central adiposity

Increased central adiposity in women is a greater predictor of heart disease, diabetes and death than generalised obesity.¹³ Central obesity is part of the metabolic syndrome, with associated insulin resistance, dyslipidaemia, hypertension and glucose intolerance.³

Does hormone replacement therapy increase body fatness?

Because weight gain is a feature of ageing, women taking hormone replacement therapy (HRT) may assume that any weight gain is a result of the HRT. In reality, while weight gain is usual with time, it is not related to hormone administration: the Prospective Estrogen and Progestin Intervention (PEPI) study³ showed a similar mean increase in body weight in menopausal women receiving HRT and those receiving placebo.¹⁴ Longitudinal data from 418 women in the Massachusetts Women's Health Study also showed no relationship between weight gain and menopause or HRT.¹⁵ However, it is notable that increases in weight were significantly related to smoking cessation and discontinuation of exercise. As smoking cessation is probably the major positive lifestyle change women can make, health professionals should provide reassurance and support throughout the process.

What information and advice should be given?

Women should be informed of the metabolic and cardiovascular risks that accompany central obesity and how the withdrawal of oestrogen during menopause may promote redistribution of fat. Overall weight gain results mainly from decreasing activity with age and can increase both general and central fatness. The decrease in physical activity with age need not be inevitable; women should be encouraged to maintain physical activity, even if there are some limitations (such as arthritis). Australia's national physical activity guidelines recommend that adults accumulate at least 30 minutes of moderate intensity activity (eg, moderate-paced walking) on most -- preferably all -- days of the week.¹⁶

The tendency to central fat deposition related to oestrogen deficiency can be attenuated by HRT; support programs to help minimise weight gain with smoking cessation are vital, especially in women with pre-existing weight problems. Much disinformation and mythology surrounds menopause and women need more scientifically sound information to help them make appropriate lifestyle and treatment decisions.

Many women have fought weight problems all their lives. Eating disorders and depression may be worsened by severe dieting;¹⁷ sensible eating habits (see Box 3, question 9) for the rest of one's life should be encouraged rather than "quick fix" diets.

Summary Weight gain in midlife is common among women. Weight gain is associated with age, not menopause. Decreasing physical activity and smoking cessation are major factors in weight gain with age.

References

1. Poehlman ET, Toth MJ, Gardner AW. Changes in energy balance and body composition at menopause: a controlled longitudinal study. Ann Intern Med 1995; 123: 673-675.
2. Svendson OL, Hassager C, Christiansen C. Age- and menopause-associated variations in body composition and fat distribution in healthy women as measured by dual-energy x-ray absorptiometry. Metabolism 1995; 44: 369-373.
3. The Writing Group for the PEPI Trial. Effects of estrogen or estrogen/progestin regimens on heart disease risk factors in post-menopausal women: the Postmenopausal Estrogen/Progestin Interventions (PEPI) trial. JAMA 1995; 273: 199-208.
4. Carey DG, Nguyen TV, Campbell LV, et al. Genetic influences on central abdominal fat: a twin study. Int J Obesity 1996; 20: 722-726.
5. Samaras K, Spector TD, Nguyen TV, et al. Genetic factors determine the amount and distribution of fat in women after the menopause. J Clin Endocrinol Metab 1997; 82: 781-785.
6. Samaras K, Kelly PJ, Chiano M, et al. Genetic and environmental influences on total and central abdominal fat. The effect of physical activity in female twins. Ann Intern Med 1999; 130: 873-882.
7. Hu FB, Sigal RJ, Rich-Edwards JW, et al. Walking compared with vigorous physical activity and risk of type 2 diabetes in women. A prospective study. JAMA 1999; 282: 1433-1439.
8. Davy KP, Evans SL, Stevenson ET, et al. Adiposity and regional body fat distribution in physically active young and middle-aged women. Int J Obes Relat Metab Disord 1996; 20: 777-783.
9. Brochu M, Starling RD, Ades PA, Poehlman ET. Are aerobically fit older individuals more physically active in their free-living time? A doubly labelled water approach. J Clin Endocrinol Metab 1999; 84: 3872-3876.
10. Rebuffe-Scrive M, Lonnroth P, Marin P, et al. Regional adipose tissue metabolism in men and postmenopausal women. Int J Obesity 1987; 11: 347-355.
11. Samaras K, Spector TD, Kelly PJ, Campbell LV. Tobacco smoking and estrogen replacement therapy are associated with lower total and central fat in monozygotic twins. Int J Obesity 1998; 22: 149-156.
12. Haarbo J, Marslew U, Gotfredsen A, Christiansen C. Postmenopausal replacement therapy prevents central distribution of body fat after the menopause. Metabolism 1991; 40: 1323-1326.
13. Manson J, Willett W, Stampfer M, et al. Body weight and mortality among women. N Engl J Med 1995; 333: 677-685.
14. Vanhala MJ, Pitkajarvi TK, Kumpusalo EA, Takala JK. Obesity type and clustering of insulin resistance-associated risk factors in middle-aged men and women. Int J Obesity 1998; 22: 369-374.
15. Crawford SL, Casey VA, Avis NE, McKinlay SM. A longitudinal study of weight and the menopause transition: results from the Massachusetts women's health study. Menopause 2000; 7: 96-104.
16. National physical activity guidelines for Australians. Canberra: Commonwealth Department of Health and Aged Care, 1999.
17. Allaz AF, Bernstein M, Van Nes MC, et al. Weight loss preoccupation in aging: a review. J Nutr Health Aging 1999; 3: 177-181.

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