Why and how does body fat distribution change as you age

One of the more observable changes that occur as you journey through life are changes to your body shape. For those who are blessed with good genes and an active lifestyle, these changes may be more subtle. However, changes to body fat distribution are a common part of the aging process and can impact your health and quality of life.

Phrases like beer belly, the middle age spread, or apple shape are often used to describe the tendency to store more fat in the abdominal region as we age.  Visceral fat, or fat that accumulates in the abdominal region, is associated with health conditions such as cardiovascular disease and diabetes. Loss of muscle and bone density can lead to reduced strength and balance, and this can lead to falls and breaks as we reach old age.

How does body fat distribution change as you age?

Generally, body fat increases gradually from the age of 30 – we start to lose lean muscle tissue and bone density, whilst gaining fat. This becomes more noticeable after the age of 40, where it can become increasingly harder to lose weight.

Men and women undergo different body composition changes during aging. Commonly men gain weight until the age of 55, then later begin to lose weight.  Women gain weight until the age of 65 and then start to lose weight. Losing weight later in life is often attributed to loss of lean muscle tissue, which is replaced by fat, which weighs less¹. 

The distribution of body fat changes, with an increase in abdominal and trunk fat and a reduction in fat located in the limbs².

Lean muscle mass generally contributes up to about 50% of total bodyweight in young adults but decreases with age to be about 25% of total bodyweight by age 75–80 years³. Older men have larger skeletal muscle mass, while older women have larger fat mass⁴.

Why does body fat distribution change as you age?

There are several reasons why body fat distribution changes through the aging process. Genetics plays a significant role and, if the majority of your family have a tendency towards gaining weight in the abdominal and hip area, then chances are that you will follow suit. Gender, hormonal changes, slowed metabolism, muscle loss, health conditions and lifestyle all have an impact.

Muscle loss

Sarcopenia, or muscle loss, associated with aging starts as early as your 30s, as you can lose 3-5% muscle mass per decade. Men tend to lose around 30% of their muscle mass over their lifetime⁵.

Reduced exercise levels as you age contributes to muscle loss and weight gain, as we burn less calories through exercise and reduced muscle mass. Lean muscle increases calorie expenditure and so, the less muscle you have, the fewer calories you burn. 

Metabolism

Resting metabolic rate (RMR) describes the amount of calories that your body uses to perform basic bodily functions, such as breathing, digesting and circulation. The number of calories required is calculated by the physical energy that you expend each day, plus your RMR. 

RMR reduces as you age and your body requires less calories to function. This is thought to be attributed to reduced muscle mass and a reduction in the size of organs associated with metabolic rate. This contributes to changes in body composition, contributing to reduced lean mass and increase in body fat⁶.

This reduced caloric requirement means that, even if you maintain the same diet and exercise habits, you can gain more body fat than when you were younger.

In addition to needing less calories, changes occur in your lipid turnover, the way that your body removes and stores fat in the body. In a study that followed 54 men and women over 13 years, participants were found to have a reduced lipid turnover rate, whether overall they gained or lost weight over this time. For those who didn’t reduce caloric intake, they gained weight by an average of 20%⁷.

Hormonal changes

Declining levels of certain hormones, such as testosterone in men, or oestrogen in women, contribute to weight and body composition changes as you age.

As women approach menopause, a transitional time, known as peri-menopause, oestrogen and progesterone levels decline. This causes a variety of symptoms for women in their 40s to 50s. Hormonal changes, changes in sleep patterns and microbiome composition are associated with increased appetite and fat mass, accumulating particularly in the abdominal region⁸. 

What can you do about it?

Age related weight gain can be frustrating, particularly if you have made some lifestyle changes to no avail. There are lifestyle and dietary changes that you can try, including:

• Stress management – as you age stress management becomes more important, for many reasons, including weight gain. Stress is a key contributor to the accumulation of visceral fat and just reducing your stress levels can be hugely beneficial. You could consider meditation, getting into nature, or mindful practices such as Tai Chi, Qi Gong, or spending time in nature.
• Exercise – incorporate strength training into your exercise regime. This is more important as you age, as maintaining muscle mass improves metabolism, balance and strength, reducing the risk of falls.
• Diet – avoiding processed foods and eating a wholefoods diet is important throughout your lives and remains so as you age. You should ensure that you are getting adequate protein to support muscle mass. This requirement changes as you age and in your 40s and 50s is around 0.8 grams of protein per kg of your weight. A woman weighing 72kgs should aim for 58 grams of protein per day.

 

Suzy Walsh 

BBA (Hons)., BNat., mNMHNZ

Registered Naturopath & Medical Herbalist

References:

¹ Aging changes in body shape: MedlinePlus medical encyclopedia. (n.d.). MedlinePlus - Health Information from the National Library of Medicine. https://medlineplus.gov/ency/article/003998.htm

² Ponti, F., et al. (2020). Aging and imaging assessment of body composition: From fat to facts. Endocrinol, 14 Jan 2020, Endocrinology of Aging. doi: 10.3389/fendo.2019.00861

³ Kalyani, R. R., Corriere, M., & Ferrucci, L. (2014). Age-related and disease-related muscle loss: The effect of diabetes, obesity, and other diseases. The Lancet Diabetes & Endocrinology, 2(10), 819-829. https://doi.org/10.1016/s2213-8587(14)70034-8

⁴ Kim, S., & Won, C. W. (2022). Sex-different changes of body composition in aging: A systemic review. Archives of Gerontology and Geriatrics, 102, 104711. doi: 10.1016/j.archger.2022.104711

⁵ Preserve your muscle mass. (2016, February 19). Harvard Health. https://www.health.harvard.edu/staying-healthy/preserve-your-muscle-mass

⁶ St-Onge, M., & Gallagher, D. (2010). Body composition changes with aging: The cause or the result of alterations in metabolic rate and macronutrient oxidation? Nutrition, 26(2), 152-155. doi: 10.1016/j.nut.2009.07.004

⁷ Arner, P., et al. (2019). Adipose lipid turnover and long-term changes in body weight. Nature Medicine, 25(9), 1385-1389. doi: 10.1038/s41591-019-0565-5

⁸ Fenton, A. (2021). Weight, shape, and body composition changes at menopause. Journal of Mid-life Health, 12(3), 187. doi: 10.4103/jmh.jmh_123_21