Why do we get belly fat as we approach menopause?

It is very disconcerting to start putting on belly fat as you get older – especially when you have been diligent in your diet and exercise program.  Yet this is a very common experience for women in their mid and late forties.  Why does this happen?  Some interesting research over the last ten years has been shedding light on this.

It starts with perimenopause

Menopause is the point in time when the ovaries no longer produce estrogen and progesterone.  The average age of menopause is 52.  However, starting several years before this, women go through perimenopause.  This happens anywhere from four to ten years prior to the actual menopause.  During this time the ovaries start winding down – ovulation becomes infrequent, and the hormone levels gradually decline.  In response to the low estrogen levels, the brain sends out chemical messengers – the main one being follicle stimulating hormone (FSH) – that go to the ovaries to try to get them to start working again. However, since the ovaries can’t respond to this prodding, the brain keeps sending out more and more FSH.  The characteristic hormone changes that occur in perimenopause are outlined on the graph below. There are rising levels of FSH and declining levels of estradiol – the principal estrogen made by the ovaries.

Estrogen effects on fat

Prior to puberty, there is not much estradiol produced by the ovaries.  However, as girls transition through adolescence, large amounts of estrogen are generated.  Estrogen triggers many changes, such as stimulating the growth of the uterus and the appearance of armpit and pubic hair.  It also influences where fat gets deposited.  Under the influence of estrogen, fat accumulates in the breasts and hips, generally sparing the midsection.  This is what transforms a young girl’s figure into the hourglass shape of a woman.

As women approach menopause, the reverse happens.  Without estrogen’s influence, a woman’s breast size tends to decrease, hips and thighs become less prominent, and the amount of fat around the waist increases.  This not only shows up as visible belly fat, but fat accumulates inside the abdomen where it lays within and on top of the internal organs.  This form of fat deposition is referred to as visceral fat.

The brain’s role in belly fat

While the effects of estrogen on fat deposition have been known for a long time, we now know there is even more to the story.  The high levels of FSH play a role.  We used to think that FSH was only responsible for promoting ovulation and a successful pregnancy, but FSH has effects on other areas in the body, such as the bones, the arteries, and the fat cells.  It is now recognized that the high levels of FSH that show up in perimenopause and menopause are partly responsible for the appearance of belly fat.

Scientists have been able to block FSH in lab mice and they found that these mice didn’t gain abdominal fat.  Similarly, they injected FSH into mice and found that this led to central weight gain.  Other studies in humans have shown that women who have the highest FSH levels in perimenopause and after menopause tend to have more belly fat.  More research in this area is forthcoming, but you can imagine that there may be some weight loss drugs related to FSH in the future!

The health effects of belly fat

Besides being unwelcome, the increase in fat around the middle is undesirable for other reasons.  Fat cells in and around the abdomen turn out to be metabolically active.  This means that they do other things besides just being storage containers for fat molecules.  They produce various chemicals that can have negative health consequences – such as promoting inflammation and interfering with the way our bodies process blood sugar and cholesterol.  The end result of this is that the more abdominal fat a person has the more prone they are to heart disease and diabetes.  That is why you may have heard that having an apple shape (being wider around the middle than the hips) is not as healthy as having a pear shape (being wider around the hips than the waist).

Many health-screening calculators use waist circumference to help assess a person’s risk for future health issues.  Calculating your waist-to-hip ratio (WHR) is a quick and easy way to monitor how much abdominal fat you carry.  To do it, stand up straight, legs close together, with weight evenly distributed across your feet; don’t suck in your belly.  After breathing out, measure the smallest part of your waist, usually just above the belly button, with a tape measure.  Then measure the widest distance around your buttocks to get your hip number.  The tape should be held snugly around the body but not be constricting, and it should be parallel to the floor.

To get your WHR, divide the waist circumference number by the hip circumference.  Though values vary, a healthy WHR (low risk) is generally defined as 0.95 or lower for men, and 0.80 or lower for women.  A WHR of 1.0 or higher in men and 0.85 or higher in women means you have excess abdominal fat and are at increased risk for heart disease and other conditions.

Could having belly fat ever be a good thing?

Even though we are understanding the biology of why belly fat develops in women, the question arises as to why nature took this course. It is interesting to speculate.  Studies have shown that the propensity for developing an apple shape is partly driven by genetics and that many people in the world have these genes.  This would suggest that these genes would confer some sort of evolutionary advantage.

One reason may be that women who have an apple shape are much better at storing fat, than burning fat.  So they tend to require fewer calories to function.  In days gone by, life wasn’t so easy.  So it would make sense for women who no longer are bearing and raising children be in a situation where their bodies did not need to consume so much fuel.  This would leave more calories for the younger members of her clan.  In today’s society, however, where we generally have good access to food and tend to have a sedentary lifestyle, this is not such a good thing, and having an apple shape leads to health consequences and weight gain.

The bottom-line

The bottom-line is that for most women, it is inevitable that there will be a redistribution of fat toward the middle, even if there is no weight gain or change in activity.  It can be difficult and frustrating to prevent this.  The best approach is to be as proactive as possible by intensifying efforts toward a healthy lifestyle.  This would include cutting down on extra calories and committing to a regular exercise program.  Aim for at least 30 minutes aerobic exercise five times a week.  In addition, stay as active as possible – such as using the stairs instead of elevators, getting up and moving throughout the day, and engaging in active rather than sedentary recreational activities.  Adding in a moderate weight-strengthening program two or three times a week is also helpful because muscle tissue tends to burn more calories than fat tissue.

What about estrogen replacement?

Based on the information I have presented it would seem logical that taking estrogen replacement at the time of menopause would be helpful.  Not surprisingly this appears to be the case.  Extensive studies in mice and rats have clearly demonstrated that estrogen treatment prevents abdominal fat.  There has also been research in the lab showing that administering estrogen to human visceral fat cells prevents them from storing fat.

Despite this, there have been very few studies in women.  However, those that have been published have shown that women taking estrogen at the time of menopause have less central fat accumulation.  Even the most famous study on HRT, the Women’s Health Initiative, reported that women on HRT had slimmer waist circumferences.  However, the current guidelines caution doctors not to recommend hormone replacement therapy solely for the control of body fat. This is because there continues to be debate regarding whether the overall benefits of HRT outweigh the risks.

Fortunately, estrogen therapy is recommended as a treatment for hot flashes.  For women contemplating treatment with HRT for this reason, the fact that it will likely help prevent belly fat should be taken into consideration.