Why do we tend to gain weight as we get older?

I have heard many times from new clients that they felt the weight-gain they experienced as they got older was because they assumed that their body’s metabolism was slowing down. But that is not true luckily. While there is a slight decrease in energy burned as we get older, it is not as much as most people think.

Here you will find an article from ZOE, which is a device that tracks your glucose levels throughout the day. They explain on their website that it has been shown that metabolism stays pretty consistent over our adult lives. Between the ages of 20 and 60 there is actually little difference in our metabolic rate. After 60 that drops by less than 1% per year, which is still quite a small change.

So why do we tend to gain weight as we get older, then?

The answer lies in body composition, meaning the ratio of muscle and fat that our body carries.

From 30 onwards, if you don’t do any regular exercise, especially weight-lifting, a few times a week, you end up losing muscle. Muscle is a “use it or lose it” type of tissue and it is very expensive (calorically) for the body to keep. Our bodies always look for ways to save energy as a survival mechanism, which results in letting go of unused muscle. If you’re not using your muscles regularly then it is not really necessary to keep them. Or so the body thinks.

Furthermore, muscle burns energy just by existing. Fat does not. If you weigh 80kg and you are 15% body-fat you don’t have the same body as someone who weighs 80kg with 30% body fat. Your lean mass, meaning your weight without fat, is much higher at 15%. You would have a lot more muscle. Which means you also burn more calories every single day. By quite a big margin.

Over the years, most people tend to not train enough, or at least, efficiently enough to maintain a good body composition. So year after year their muscle mass will slowly diminish while their body-fat usually rises. Over decades this effect can be amplified to disastrous consequences for our metabolism. Ultimately, you may weigh the same at 50 as when you were 30, but that may not reflect what is really going on within you.

Muscle is the answer. Your resting metabolic rate, or, energy burned without counting activity, will always be higher when you build and maintain a solid ground of muscle tissue. And, for that reason, it will be a lot easier to stay lean and strong later in life if you do weight-lifting, which is what muscle needs to be able to stay.