Middle age weight gain – It’s not your metabolism

You can easily blame the increase in belly fat in middle age (45-65) due to a slowing metabolism.  However, this does not see to be true.  Research by Herman Pontzer at Duke University has shown that metabolism really doesn’t change between the ages of 20 and 60.  So why is it so much easier to gain weight after 45?  The answer may be primarily due to these 5 factors:


As you get older, your normal oestradiol levels (especially pre-menopause) reduce. Your estrogen naturally inhibits the growth of belly fat and increases deposit around the hips and thighs.  In men, up to 25% of men have low testosterone (over 45).  This can be due to a range of causes, including, excessive alcohol intake, kidney disease, medication, obesity and diabetes.  Low testosterone in men is also paralleled with a reduction in estrogen levels (Yes, men have estrogen as well). Low testosterone in men means a reduced muscles mass (affecting your metabolism), therefore supplementation may be needed.  However, supplementation is only effective if you have low testosterone.  Supplementing testosterone if you have normal level will reduce your natural production, so see your doctor first.  For both men and women, it is important to have your sex hormone levels check regularly.

Stress and Cortisol

Stress leads you to increased release of your natural stress hormone, cortisol. Cortisol’s effect is weight gain and increased hunger.  An increased cortisol level will cause you to choose to eat more, especially unhealthier options leading to  more weight gain.  Middle age seems to be one of the highest stress times of your life, with the dual stress of takes care of children and aging parents.  There is no easy answer when you feel like “you are being pulled in all directions”.  However, finding a way to manage stress by have some time to “enjoy” life has a direct effect on helping manage your weight

Sleep Deprivation

Reduced regular sleep has the direct effect of reducing Leptin (the natural hormone to feel full) and increasing ghrelin (the hormone to feel hungry). Sleep deprivation also triggers high levels of endocannabinoids, natural lipids that increase your satisfaction from eating food.  As a result, you tend to eat more, crave food more and make unhealthier choices.  Again, although this is not easy, but good sleeping habits are an important part of your weight management strategy.

Reduced Thyroid Function

About 5% of people have an underactive thyroid (hypothyroidism). This can develop over time and leads to a reduction in the hormone thyroxine.  Thyroxine directly affects your metabolism.  It is very difficult to manage your weight with low thyroxine levels.  See your doctor to get your levels checked and manage if appropriate.

Healthy muscle mass

Mass muscle has a direct effect on your metabolism. It is the one major aspect of your basal metablic rate you can influence.  Having a regular and structured strengthening program will help maximise your muscle mass.  In addition, starvation diets and skipping meals reduces your muscle mass.  Although these approaches may have a short term affect on your weight, they reduce your muscle mass.  Your will use your muscles a source of protein and energy, resulting in an overall reducing metabolism in the long term.  Lower musle mass makes it harder to manage and control your weight

Interestingly, none of these factors are independent and affect each other.  Reduced sleep leads to increased stress.  This leads to increased cortisol release and reduced muscle mass, a difficult cycle to break.

However, take the first step and these important practical tips in managing your weight in middle age.

Novak, S (2022) Battle of the mid-life bulge, 12th March 2022, No. 3377.  P38-41.

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