What Happens To Your Metabolism After 30?

What Happens To Your Metabolism After 30?

When you’re younger, it feels like you can eat as much pizza and ice cream as you want and not see the effects of it sitting on your hips a day later. But as we reach the end of our twenties, some of us can’t even sniff a burger without it going straight to our chins. We all know our metabolism changes as we get older, but how much does it really affect you once you’re in your thirties?

Firstly, what is metabolism? 

According to Matt Durkin, a nutritional specialist at Simply Supplements, our metabolism is "a set of critical chemical reactions that happen within the cells of your body. It has three key elements: the breakdown of food into energy (catabolism); the conversion of food into ‘building blocks’ such as protein into muscle (anabolism); and the removal of metabolic waste products such as carbon dioxide. The sum of these elements dictates how many calories we require per day."
The human metabolic rate is influenced by four key factors:

  1. Basal Metabolic Rate (BMR): How many calories we burn at rest. This can be influenced by age, gender, muscle mass, fat mass and hormones.
  2. Thermic Effect of Food (TEF): How many calories it requires to digest and absorb the food we eat. Fat has the lowest TEF, carbs have a medium TEF and protein has a very high TEF. Therefore, a high protein diet can modestly increase metabolic rate.
  3. Non-Exercise Activity Thermogenesis (NEAT): How many calories are burned from activities such as standing up, fidgeting and household chores.
  4.  Exercise.

Is it true our metabolism drops when we reach our thirties? By how much?

Thirty is often cited as the age that our metabolism officially slips, but Dr. Holly Lofton, director of medical weight management at New York University Langone Health says that our metabolisms actually start to slow at age 25, by around 2% per decade – it’s just we don’t notice the change until our 30s. “[Metabolism actually decreases almost linearly with age,” she told The Cut. “The reason 30 is an important decade is because that’s the first decade in which we’re no longer increasing in bone production. So if we don’t increase muscle-mass production, overall metabolism goes down.” This means, because we’re no longer having growth spurts, even little ones, our bodies quickly accrue fat which, unless we turn it into muscle mass, will cause weight gain.  

As for the 2%, in terms of calories that can be anything from 50 to 70 calories a day. “For example, a 70kg man aged 18-29 is estimated to have a Basal Metabolic Rate of 1740kcal per day. But a 70kg man aged 30-59 is estimated to have a BMR of 1670kcal. So that’s a difference of 70 calories per day.” This means as you age, the need to increase activity or reduce calorie intake is likely needed to maintain your pre-30s weight – although scientists have long debated the merits of counting calories.


Should we accept weight gain in our thirties simply as our metabolism slowing down?

Matt says our lifestyle choices can have a significant impact on our metabolic rates. "As we age, we start to lose muscle mass, which can influence metabolism," he says. "Furthermore, older adults tend to be less active than their younger selves. This is important, as this doesn’t just mean the calories burnt through exercise is lower, it also means we use our muscles less, leading to muscle loss.

"The end result is that we shouldn’t accept weight gain as a sign of our body working against us. Instead it should stimulate us to look at our lifestyle to see what we could be doing differently."

Matt’s top 3 tips for speeding up your metabolism in your thirties…

  • Up your protein intake: This will help you feel fuller for longer which, in turn, can lead to a lower overall calorie intake. Protein also supports the maintenance (or growth) of muscle mass, whilst modestly increasing your metabolic rate. Maintaining optimum nutrition can be tricky as you get older, so daily vitamin supplements might be the answer for you.
  • Take up calorie-burning habits: Such as standing instead of sitting, or taking the stairs instead of the lift, and incorporate them into your everyday routine.
  • Mix aerobic & resistance workouts: Aerobic exercise helps to burn off excess calories, so now is the perfect time to start jogging or cycling again. Resistance training is equally important too, as it supports muscle mass and strength, helping to ensure good metabolic health.

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