An article on why do we gain weight as we get older

Why do we gain weight as we get older?

This is the age-old question. Why do we gain weight as we get older?

Back when you were young, you could eat whatever you want and not gain an ounce. Now, you just look at a bar of chocolate and you gain 5 pounds overnight. Or is that so?

This article is going to look into the real reasons as to why we gain weight as we get older.

You hear stories of how your metabolism crashes when you reach a certain age or how your body is unable to process food in the same way.

Like most of these claims, there is little truth to this myth. But as usual, that truth has been stretched excessively.

So, I will go over the reasons as to why we gain weight as we get older and what we can do going forward.

The reasons we gain weight as we get older are:

  • Less active
  • Muscle breakdown
  • Increase in eating
  • Sleep/Stress
  • Alcohol

Decrease in activity

This may seem obvious but it’s really understated.

Think about it children, and teens, spend their break times and lunchtimes outside running about. Many also are part of sports clubs too. All these activities burn hundreds of calories every day.

As soon as we reach adulthood, breaktimes and lunchtime aren’t spent running about. They’re spent looking at Facebook and Instagram on your phone, whilst enjoying a snack.

However you look at things, as we get older, we move about less.

To combat this decrease of activity, I recommend increasing your levels of NEAT. That way you don’t need to actually worry about having to go running or taking up a sport.

To increase your NEAT. I advise you get a pedometer. From there you can work out your average step count. Then from then on, you can work on gradually increasing it. If you can get it up higher than 8000 steps a day, you’ll be in the right direction. (1)

Muscle breakdown

Though inactivity is one of the biggest culprits of adult weight gain. Muscle breakdown also plays a role.

Most people claim their metabolism slows down as they age. It’s true to the extent that most adults, do burn slightly fewer calories as they get older. But the number is so small, you can’t really claim your metabolism is crashing.

However, the reason people burn fewer calories as they get older is that after the age of 30, the body starts to break down its muscle tissue. (2)

If your body doesn’t use its muscle, the body sees no reason to keep it, therefore it goes. But if you’re still eating the same number of calories, your body will replace that muscle tissue with fat.

Fat is less metabolically active than muscle. This is a fancy way of saying, the same mass of muscle will burn more calories than the same mass of fat. (3)

A simple resistance training programme and increasing your protein intake will more than take care of that.

Increase in food autonomy

Now you’re an adult, you can literally eat whatever you want. Nobody dictates what you should eat, so if you want to eat fast food all day every day you can.

When you’re at work, you don’t have your parent or teacher telling you, no you can’t have that chocolate from the vending machine.

I have noticed as well coming into adulthood, priorities change. When you’re young, priorities involve going out and playing sport etc. But when you’re in adulthood 99% of your conversations involve food, free time usually involves food, your life tends to now revolve around what you’re going to eat next.

When you’re young, eating is a slight inconvenience, it gets in the way of having fun. As an adult eating is your fun and everything else is an inconvenience.

As adults life revolves around food. Trying new foods is deemed exciting and not intimidating like it was when younger.

Last but not least, we tend to eat past the point of fullness.


Being an adult is significantly more difficult than being younger. Whether it’s dealing with children, relationships, work, family etc. These can all lead to a build-up of stress and a lack of sleep.

An increase in stress is linked to having greater levels of the hormone cortisol, which makes regulating appetite and the eagerness to exercise more difficult. (4,5)

When you’re younger, your sleep time was most likely to be scheduled and you were more likely to sleep the amount of time needed.

  • As an adult a lack of sleep can happy for many reasons:
  • Stress
  • Dealing with baby/toddler
  • Too much caffeine
  • Shift work
  • Too much screen time

There is a link between those who sleep less and be more likely to carry more excess fat. (6)

A study in 2004, with 1024 participants found; that those who had short sleep durations hunger hormones were altered. Their levels of leptin had reduced and levels of ghrelin had increased. This study showed there was a greater correlation with higher BMI in people that slept less than 7-8 hours.

  • Ghrelin – increases hunger
  • Leptin – tells the body it’s full

Therefore it’s theorised that these hormones, drive hunger, thus meaning people eat past the point of fullness, which will lead to weight gain. (7)


Finally, we have alcohol. Many of us like to wind down with a drink. Something we weren’t doing when we were younger, I hope.

However, drinking can lead to excessive weight gain in many ways.

  • Alcohol contains 7 calories per gram
  • Alcohol is not satiating
  • Binge drinking leads to reduced and poorer quality sleep
  • Alcohol reduced inhibitions
  • Reduces motivation to exercise

For every gram of alcohol consumed, it comes with 7 calories. This is why alcohol-free beers to end contain half the calories, of their alcohol counterparts. This is a lot of calories, which could be going to food, which will fill you up. It’s also been shown people don’t reduce their usual food intake when drinking, therefore the alcohol consumed from calories, is extra that gets added up. (8)

As well as the added calories from alcohol, a lot of alcoholic drinks are mixed with high sugar mixers. Many cocktails contain up to 490 calories per drink. A few of them on a night out really do add up and won’t fill you up, as a meal would. (9)

A 2020 study in China, with 11,905 people, was used to see how alcohol intake affected sleep. They were split into 4 groups.

  • Non drinking
  • Light drinking
  • Moderate drinking
  • Heavy drinking

Long story short. The higher the amount of alcohol consumed, the shorter and poorer the quality of sleep. (10) As mentioned in the chapter above, a lack of sleep will increase your hunger.

When it comes to inhibitions towards food, alcohol seems to kill that. Think of the munchies you get when drunk. The reasons for this are also not fully understood. But there are some reasons drinking could increase hunger.

Lower inhibitions – Being drunk lowers your inhibitions, so when you may have said no to those chips you really wanted, drunk you will say yes. (11)

Finally, it’d harder to exercise after a night of drinking. When I used to drink, I’d be lucky to do 1000 steps on a hangover day. As for proper training, no way that would happen. Long story short, your energy expenditure is most likely to tank, if you’ve been drinking heavily the night before. (12)

Final thoughts

So why do we gain weight as we get older? This is not as simple as your metabolism just crashing. The evidence shows, even with muscle loss, the number of calories you burn per day, doesn’t decrease that much. However, there are plenty of other factors, which do have an impact.

Your life is different, you’re most likely bound to a desk 8 hours a day. You don’t spend your lunchtime running around and participating in lots of sports, as you may have before.

If alcohol is part of your life, that is something else, that will influence the number of calories you take and most likely bring down the number you burn per day. You can have alcohol and fit it, in your calories. But you must accept it will make things a little more difficult.

So what this article explains is; if you can manage to improve your sleep, increase your activity, lift some weights, eat a bit more protein and watch your food intake. You’ll realise your metabolism is fine and you just needed to slightly adjust to your new lifestyle.

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