Does Body Fat Go Up with Age? The Science Behind Age-Related Fat Gain

According to one review, between the ages of 25 and 65, the percentage of body fat in both men and women tends to increase. While total body weight may not change significantly during these years, shifts in body composition mean that many adults see an increase in fat mass and a corresponding decrease in lean muscle mass, raising the question: does body fat go up with age?

Quick Summary

Body fat typically increases with age due to a combination of slower metabolism, muscle loss (sarcopenia), and hormonal changes. This often results in a redistribution of fat toward the midsection and internal organs, even if overall weight remains stable.

Key Points

• Body fat typically increases with age: Most individuals experience a gradual increase in body fat percentage from middle age onward, even if total body weight remains stable.

• Metabolism slows down with age: The loss of muscle mass (sarcopenia) and a decline in basal metabolic rate mean the body burns fewer calories, making fat gain more likely if diet and exercise remain unchanged.

• Hormonal changes drive fat redistribution: Declining estrogen in women and testosterone in men contributes to a shift in fat accumulation, especially around the midsection as visceral fat.

• Visceral fat increases health risks: Fat accumulation around internal organs (visceral fat) is a concern with age, as it is linked to a higher risk of heart disease and diabetes.

• Strength training is a primary defense: Resistance exercise is critical for building and preserving muscle mass, which helps counteract the metabolic slowdown and keeps body fat in check.

• Lifestyle factors are controllable: Diet, exercise, sleep, and stress management are major factors influencing body composition with age and can be proactively managed to mitigate fat gain.

• Protein intake becomes more important: As people age, their protein needs may increase to help stimulate muscle protein synthesis and combat muscle loss.

Understanding Age-Related Changes in Body Composition

As we grow older, our bodies undergo a complex series of changes that affect our body composition, or the ratio of fat mass to lean mass. A defining characteristic of aging is an increase in fat mass, often concentrated in the abdominal area, and a decrease in muscle mass. These shifts happen gradually and are influenced by a mix of biological and lifestyle factors.

Why Metabolism Slows Down

One of the primary drivers of age-related fat gain is a slower metabolic rate. Resting metabolic rate (RMR), the energy your body burns at rest, decreases as you get older. This is largely due to the concurrent loss of muscle mass, known as sarcopenia, which begins as early as age 30. Since muscle is more metabolically active than fat, having less muscle means your body requires fewer calories to maintain itself. If your caloric intake doesn't decrease to match your lower energy expenditure, the unburned calories are stored as fat.

The Impact of Hormonal Changes

Fluctuating hormone levels also play a significant role in body composition shifts, and these changes differ between men and women.

In women:

• Estrogen and progesterone levels drop during and after menopause.
• This hormonal shift contributes to an increase in abdominal or visceral fat, even if a woman doesn't gain overall weight.
• The decline in estrogen also affects where fat is stored, encouraging fat redistribution towards the abdomen instead of the hips and thighs.

In men:

• Testosterone levels decline gradually over time.
• Decreased testosterone can lead to a loss of muscle mass and an increase in body fat, particularly around the midsection.
• This lower testosterone can also contribute to reduced energy and motivation, further hindering physical activity levels.

The Role of Physical Activity and Lifestyle

Lifestyle choices and habits, or the lack thereof, significantly contribute to whether body fat increases with age. A more sedentary lifestyle, which is common as people age, reduces calorie burn and accelerates muscle loss. Maintaining regular physical activity, especially resistance training, is crucial for preserving muscle mass and boosting metabolism. Diet also plays a critical role, as higher consumption of processed foods and a failure to adjust caloric intake can lead to a positive energy balance and subsequent fat gain.

Fat Redistribution and Its Health Implications

It's not just the increase in total body fat that is concerning, but also its redistribution. With age, fat tends to shift from subcutaneous depots (fat under the skin) to the abdominal region, accumulating as visceral fat. Visceral fat surrounds the internal organs and is linked to a higher risk of chronic diseases, including type 2 diabetes and cardiovascular disease.

• Chronic Inflammation: Excess body fat, particularly visceral fat, can promote a state of low-grade chronic inflammation throughout the body. This inflammation has been linked to muscle weakness and reduced function, creating a vicious cycle.
• Insulin Resistance: The accumulation of visceral fat and the loss of muscle mass can contribute to insulin resistance, making it harder for the body to regulate blood sugar effectively.

Comparison of Body Composition Changes Over Time

Feature	Young Adult (approx. 20-30 years)	Middle-Aged Adult (approx. 40-60 years)	Older Adult (approx. 65+ years)
Muscle Mass	Peaks in the 20s and 30s.	Gradual decline of approximately 3-8% per decade begins.	Accelerated decline, potentially leading to a total loss of 30% by age 80.
Body Fat	Stable or slowly increasing.	Steadily increases, often accompanied by weight gain.	May stabilize or even decline slightly in very old age, though body fat percentage may remain high due to muscle loss.
Fat Distribution	More evenly distributed, often with higher subcutaneous fat.	Significant redistribution toward the abdomen and visceral organs.	Fat continues to accumulate centrally; loss of peripheral subcutaneous fat may occur.
Metabolism	High and efficient, with higher energy needs.	Slows down due to decreasing muscle mass and other factors.	Continues to slow, making weight maintenance more challenging.
Hormones	High and stable levels (estrogen, testosterone).	Decline begins, especially for women in menopause.	Continual decline of reproductive hormones.
Physical Function	High muscle strength and endurance.	Declines start, often masked by existing muscle.	Reduced muscle strength (dynapenia) and increased risk of frailty.

Counteracting Age-Related Body Fat Increase

While some age-related changes are inevitable, lifestyle interventions can help manage and mitigate the increase in body fat.

• Prioritize Resistance Training: Strength training is the most effective intervention to combat sarcopenia, the loss of muscle mass. Lifting weights or performing resistance exercises helps build and preserve muscle, which in turn boosts your metabolism.
• Increase Protein Intake: Older adults may need a higher protein intake to stimulate muscle protein synthesis effectively. Focusing on high-protein meals can help preserve muscle mass.
• Mindful Caloric Intake: As your metabolism slows, your body requires fewer calories. Practicing mindful eating and controlling portion sizes can help prevent a caloric surplus that leads to fat gain.
• Incorporate Aerobic Exercise: Combining resistance training with moderate-intensity aerobic exercise, such as walking or swimming, can further improve cardiovascular health, burn calories, and manage weight.
• Manage Stress and Sleep: High stress levels can increase the hormone cortisol, which is linked to weight gain. Poor sleep also negatively affects metabolism and appetite-regulating hormones. Focusing on stress management and getting 7-9 hours of sleep per night is vital.

Conclusion

In conclusion, the answer to the question, "Does body fat go up with age?" is a definitive yes for most people, though the rate and distribution differ based on sex and lifestyle. The increase in body fat is driven by multiple interconnected factors, including declining metabolic rates due to muscle loss (sarcopenia), hormonal fluctuations, and changes in lifestyle habits. This fat gain is often accompanied by a detrimental redistribution toward the abdominal area, raising health risks. However, this process is not inevitable. By actively engaging in strength training to preserve muscle mass, maintaining a balanced diet with adequate protein, and managing stress and sleep, it is possible to counteract these effects and promote healthier aging. Adopting a proactive approach to diet and exercise is key to minimizing age-related fat gain and protecting overall health and functional ability well into old age.

InsideTracker offers resources on managing age-related weight changes.

Frequently Asked Questions

Is it true that metabolism slows down with age?

Yes, metabolism does naturally slow down with age. This is largely due to sarcopenia, the gradual loss of muscle mass that occurs over time. Since muscle tissue is more metabolically active than fat, a reduction in muscle mass lowers your body's overall energy expenditure.

Why do women gain fat in their belly after menopause?

Hormonal changes are the primary reason for this shift. The decline in estrogen levels during menopause influences where the body stores fat, causing it to redistribute from the hips and thighs to the abdominal area as visceral fat.

Can exercise prevent age-related body fat increase?

Yes, regular exercise is highly effective for managing age-related fat gain, especially a combination of strength training and aerobic exercise. Strength training, in particular, is essential for preserving muscle mass and boosting metabolism, while cardio burns calories and improves cardiovascular health.

What is sarcopenia and how does it relate to body fat?

Sarcopenia is the age-related loss of skeletal muscle mass and function. As muscle mass decreases, the body's resting metabolism slows, and fat often replaces the lost muscle tissue. This results in a higher body fat percentage, even if your total weight stays the same.

Does eating habits need to change as we get older?

Yes. As metabolism slows, your body requires fewer calories to maintain weight. To prevent fat gain, it's beneficial to control portion sizes and focus on a nutrient-dense diet rich in fruits, vegetables, and lean protein, while reducing processed foods and sugars.

Is visceral fat more dangerous than subcutaneous fat?

Yes. Visceral fat is the fat stored around your internal organs and is considered more harmful than subcutaneous fat (the fat under the skin). Excess visceral fat is strongly linked to an increased risk of chronic diseases like type 2 diabetes and cardiovascular disease.

What is the best type of exercise to combat age-related fat gain?

The best approach is a combination of resistance training and aerobic exercise. Strength training builds and maintains metabolically active muscle mass, while aerobic activities like walking, jogging, or cycling burn calories and improve overall fitness.