5 Reasons We Gain Weight With Age

How to counteract the trend of gaining weight as you get older!

Updated: Monday 16 October 2023

Gaining weight with age

If you’re struggling with your weight more than you did when you were younger, you’re not alone.

It’s very common to experience weight gain as you get older, often starting to ramp up in your 20s and continuing through to middle and old-age. Several factors make weight loss efforts increasingly difficult as you age, and in the UK we’re seeing it’s far too common to creep into the “overweight” and “obese” categories more than ever before. In fact, 3 in 4 adults in England aged 45-74 are overweight or obese, according to a 2019 health survey by the NHS.[1]

Overweight and Obese Health Survey

But why is this? We’ve outlined 5 reasons why it’s harder to lose weight as you age.

1. Age-Related Muscle Loss

After the age of around 30, the amount of lean muscle on our bodies naturally begins to drop, a process known as age-related sarcopenia. If you’re not physically active, you can expect between 3% and 8% muscle loss per decade.[2] Some age-related health conditions may lead to muscle loss too, such as arthritis. Since muscle burns 2-3 times more calories at rest than fat does, losing muscle mass means your body will need fewer calories per day. Since most people don’t adjust their calorie intake, this calorie surplus will lead to fat build up.

2. Normal Hormonal Changes

Everyone experiences changes in hormone production at various stages of their lives, with some of the most significant occurring at middle-age.


As women experience menopause, typically between age 45 and 55, their oestrogen levels significantly drop and their weight distribution changes, with excess fat often accumulating around the belly. Gaining weight in this particular area carries several health risks, associated with high levels of LDL cholesterol (the “bad” kind), and increased risk of high blood pressure, cancers, diabetes and heart attacks.[3] Additionally, shifting oestrogen levels in perimenopause can cause mood fluctuations that make it harder to stick to a healthy diet and fitness plan.[4]


From the age of about 40, men experience a drop in testosterone of approximately 1% to 2% each year.[5] Testosterone plays a part in regulating fat distribution, muscle mass and strength, meaning the body becomes less effective at burning calories as production decreases. Around the same time, the production of growth hormone declines, making it more difficult to make and maintain muscle mass.

3. Slower Metabolism

With a decrease in muscle mass, your metabolism will slow to some degree, meaning your calorie intake needs to decrease accordingly otherwise your body will store more as body fat. However, metabolism is dictated by several factors other than age, such as your genes, body size, sex, and certain health conditions like hypothyroidism. Whilst a slower metabolism will mean you’ll have to watch what you eat more carefully, it doesn’t actually slow that much from just ageing; if you remain active through middle age and work to retain muscle mass, your decrease in metabolism will be very minor and won’t be the primary cause of any weight gain.[6]

4. More Sedentary, More Stressed

As we get into our 40s and 50s, with our careers often in full swing, you may find that you spend longer sitting down either commuting or at your desk, and the spare moments to go for a walk or a jog become few and far between. Life gets busy and it can be hard to keep up the step count with your younger self. Not only this, but stress levels might have risen now you have inevitably more responsibilities, perhaps you’re under more pressure at work or you have a family that relies upon you. Research suggests that with more work-related stress comes an increase in the body’s production of ghrelin, a hormone responsible for making you more hungry, leading to overeating.[7]

5. Less Time for Yourself

Here’s another contribution to weight gain that’s down to behaviour change. As we settle into adulthood, we go through some major life changes like starting a family. It’s common for that time that was previously available for exercise to be redistributed, spending time with your children and tending to the responsibilities that come with raising a family. The excuses for not exercising as much are arguably more understandable now than in early adulthood, not to mention you may have less time to prepare healthy meals for yourself so don’t have such an eagle eye on your diet.

Underweight in Later Life

It’s worth noting that it can be common, especially into old age, to start losing weight, but this isn’t always a good thing. If you become ill or experience a loss of appetite, you can become underweight, which puts you at greater risk of certain health conditions such as bone fractures should you fall. The immune system may become weakened, making you more susceptible to infections, and you might be deficient in some important vitamins and minerals. Read more about keeping your weight up in later life in this useful NHS guide.

How to Prevent Weight Gain and Lose Excess Fat

Healthy Foods

It shouldn’t come as a surprise that one of the best ways of cutting down on unwanted weight is to shift to a healthier diet, including reducing intake of fatty fast foods, sugars and other processed foods, and upping fruit and vegetable consumption. It’s also worth prioritising whole foods like grains, beans and legumes, nuts and seeds etc. as these are high volume foods that take up space in the stomach whilst not being too calorific. Just make sure that your diet is realistic and manageable otherwise there’s a lower probability that you’ll stick to it. Need some ideas? Check out our Alli/Orlistat diet plan.

Portion Control

Whilst it might be easier to consume too many calories by eating doughnuts compared to quinoa, a surplus is still a surplus. Total calorie intake is important to monitor and should be reduced so you’re operating in a calorie deficit in order to lose weight. Don’t change your portions too drastically to begin with, try cutting out 100 to 200 calories in total each day for a couple of weeks and go from there - you’d be surprised how much of a difference this change alone can make.


Being stressed out can often lead to stress eating, either as a behavioural coping mechanism in an attempt to feel better, or through hormonal changes increasing our appetite and cravings for high-calorie foods. You could go to a yoga class, have a stroll around the local park or escape into a good novel; make sure you do enough of whatever gets you feeling relaxed and at ease in between your busy schedule, to effectively manage and relieve stress.

Go for a Workout

Counteract that natural muscle loss as you age by doing some resistance exercise and keeping strong, alongside aerobic exercise like cycling. Not only will this help reduce belly fat, but the general health benefits are considerable - you’ll maintain mobility, support your immune system and feel good inside and out.

Sleep Well

Sleep is one of the fundamental, but often overlooked, pillars of health, and it can even help with weight loss. All of the factors above feed into your sleep quality and duration, and other methods (such as cutting out screen time half an hour before bed, and having consistent wake/sleep times) are important to be disciplined about. 7 to 9 hours of good quality sleep is what you’re aiming for.

Clinically-Proven Treatment

If you’ve tried all of the above and aren’t experiencing weight loss at the rate at which you’d like, weight loss treatments could be a suitable option to speed up the process. Medications containing the active ingredient Orlistat like Xenical can help to pass one-third of the fat consumed in your diet through your body without being absorbed. These treatments contain 120mg of the Orlistat and are suitable for people with a BMI of over 30 (or over 28 if you have certain other risk factors), but there are also 60mg options in the form of Alli and Orlos, which may be more suitable for those with a BMI of 28 and above with no other risk factors. Weight loss supplements like XLS-Medical Max Strength are also available for supporting your weight loss journey, and may be suitable for those with a BMI of over 25.

Toby Watson

Written by: Toby Watson

Pharmica Medical Writer

Toby (BSc) is an experienced medical writer, producing educational articles on many areas of health including sexual health, fitness, nutrition and mental health.

He particularly enjoys debunking misconceptions around heath conditions and their treatments, researching each topic in detail and writing easily-accessible content.

Find out more about how we ensure the accuracy of our content with our content guidelines.

5 Insights from Real Weight Loss Success Stories
5 Insights from Real Weight Loss Success Stories