What Does Estrogen Have To Do With Belly Fat?

No one likes belly fat since it usually is a reflection of overall elevated weight. Phrases like “pot belly,” “beer belly,” or “apple shaped” impact both our self‐image and our relationship to others. While genetics definitely has some effect, evolutionary forces are also at work here. Does the pattern of fat deposition suggest additional health risks? Why do women seem to preferentially gain belly fat during menopause?

Obesity is indeed a byproduct of evolution. The Paleolithic diet needed to support foraging and chasing down wild animals for food (and thus survival) consisted of red meat, fish, nuts, fruits, and vegetables. This diet was low in carbohydrates and high in proteins and micronutrients. In addition, the Paleolithic lifestyle was very active. In contrast, the industrial revolution brought with it cheap transportation, time‐saving machines, high‐glycemic prepackaged foods, and resultant obesity.

Unfortunately, fat deposition patterns can reflect health risks. Our superficial fat carries little health risk apart from impacting our psyche and our joints. It is the visceral fat around our internal organs and blood vessels that produces the inflammatory proteins that generate the major health risks of obesity. These intra‐abdominal fat cells with a direct effect on the liver are linked to the metabolic syndrome with a higher risk of diabetes mellitus, elevated cholesterol and lipids, and resultant cardiovascular disease.

Fat deposition changes with age and sex. Weight gain and fat deposition are similar in boys and girls until puberty. As adolescents, with boys having higher testosterone levels and girls having higher estrogen levels, girls begin to have a higher percentage of body fat. Testosterone causes higher muscle‐to‐fat ratios as well as its more masculinizing effects. Estrogen causes a typical female fat distribution pattern in breasts, buttocks, and thighs, as well as its more feminizing effects. During the reproductive years, women get additional fat deposition in the pelvis, buttocks, thighs, and breasts to provide an energy source for eventual pregnancy and lactation.

Paradoxically, in menopause, a woman's estrogen levels are inversely related to her weight. In a study of newly menopausal healthy women over a four‐year period, women showed an increase in weight and body fat (primarily as visceral adipose tissue), which coincided with a drop in estradiol levels and a decrease in physical activity and energy expenditure. In the laboratory, when female mice were surgically thrust into menopause by removing their ovaries, only those mice treated with estrogen maintained their weight while those deprived of estrogen rapidly gained weight. Why would this be? Studies have shown that estrogen incorporates crucial elements into the DNA responsible for weight control. The absence of both estrogen and these crucial elements leads to progressive obesity.

So, along with hot flashes, irregular menses, irritability, and depression in the menopausal transition, women have to deal with a tendency to weight gain and visceral body fat deposition that can affect their long‐term health. The best way to deal with this is still dietary adjustment and increased activity levels.

By James Woods, M.D.
Dr. Woods treats patients for menopause at the Hess/Woods Gynecology Practice.

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James Woods | 5/1/2015