How Your Body Shape Changes With Age

Whether you start out as an "apple" or "pear," your overall body shape will likely change as you age. This metamorphosis is due to several factors that fall into two main categories: those you can’t control, and those you can. In particular, the rate of these changes is closely connected to lifestyle factors like exercise, smoking, and diet.

That said, your body is mainly made up of several components, primarily bones, muscles, fat, and water. Changes in body composition (the relative proportion of weight made up by each of these components) typically happen with age even when there’s no overall change in body weight. For example, the amount of water your body carries is likely to decrease.

Your total body weight fluctuates according to the number of calories (energy) you consume relative to how many you burn. If you take in more than you burn off, over time, you’ll gain weight. Your body stores that extra energy as fat, rather than using it to fuel muscle. When this happens, the proportion of body weight you carry that is fat increases.

It's also important to note that muscle is more metabolically active than fat tissue, so it burns more energy. Any loss of muscle mass due to age can, over time, shift body composition and further accelerate fat gain.

Using a few quick measurements, you can get a general estimate of your approximate body fat percentage. For a more accurate measurement, you can get it tested in a lab using hydrostatic weighing or a DeXA scan.

It's not just the proportion of fat that changes over time—its location changes, too.

In women, the drop in estrogen levels that comes with menopause coincides with a shift of fat storage from the lower portion of the body (a "pear" shape), toward the midsection (an "apple" shape). This belly fat is comprised of both subcutaneous fat (under the skin of your abdomen) and visceral adipose tissue (fat that accumulates around organs deep within the abdomen).

A 2008 review by researchers from the National Institutes of Health (NIH) and Harvard University looked at data from more than 44,000 women in the Nurses’ Health Study over a period of 16 years. It concluded the women with greater waist circumference were more likely to die of heart disease and cancer than women with smaller waists. Specifically, the women who had a waist size greater than 35 inches had approximately double the risk of heart disease and cancer compared to women with a waist circumference smaller than 28 inches.

A more recent review in The Lancet looked at health outcomes in over 221,000 people in 17 countries. Study authors concluded that when predicting a population-wide risk for cardiovascular disease, simple adiposity measures (like BMI or waist-hip ratio) provide little or no additional information on cardiovascular risk when additional information is available. Still, the NIH recommends a waist circumference no greater than 35 inches for women and no greater than 40 inches for men.

In men, the drop in testosterone levels that occurs with aging likely affects fat distribution and hip circumference, both of which commonly decrease as men get older.

Both subcutaneous and visceral fat can be reduced through diet and exercise. To help prevent accumulating fat in your midsection as you age, maintain a healthy weight.

In healthy adults, skeletal muscle accounts for about 40% to 50% of total body weight. As you get older, loss of muscle tissue and strength (sarcopenia) results from decreased activity. Some researchers estimate that after age 30, adults experience a 1% loss of muscle mass each year.

Muscle burns more calories than fat, so having a smaller proportion of muscle on your body has implications for your overall weight and health, contributing to an overall loss of strength and increased disability.

Not only can you get wider as you age, you also may get shorter. A study conducted in England reported that physical stature declines at an average annual rate of between 0.08% and 0.10% for elderly males, and 0.12% and 0.14% for elderly females—which results in an approximate 2–4cm decrease in height over the course of a lifetime.

Study authors note, however, that changes in height can be difficult to predict on an individual basis. They provide evidence suggesting that a decline in muscle mass and decrease in bone mineral density may be the reason for a loss of height.

Bone mineral density peaks around the age of 30 and typically diminishes from there. You can help reduce lost bone density by avoiding tobacco, consuming adequate calcium, and including weight-bearing exercises like resistance training in your activity plan.