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Your Metabolism, and When it Slows Down

Let’s talk about this hot topic, because ever since I was little I have heard that, #1 squats are bad for your knees, #2 carbs are bad for you, and #3 once I hit a certain age, my metabolism is going to slow down. When I was 16-18 I heard it would be when I got out of college, when I got out of college it was when I hit my late 20s, and now it’s when I hit my 30s. Same thing with the squats thing, I hear “Just wait” a lot. Anyways, to further understand when our metabolisms actually slow down, let me tell you how your metabolism affects weight loss in the first place.

Weight loss, in general, is a very easy concept…. Burn more calories than you eat. But if it were that simple in application, everyone would be in better shape and the US obesity rate wouldn’t be going up every year [1]. To keep things on the simple side, your metabolism is all of the chemical processes your body goes through, in order to keep you alive. The food we eat has calories, and calories are literally just a measurement of energy (look up law of thermodynamics as well). So, by eating, we literally are giving our bodies the energy it needs to perform even the most basic functions of human life like breathing, pumping blood, cell production, temperature regulation, etc. This is important because a lot of people tend to think they don’t need to eat at all, or eat very very little in order to lose weight, but by doing so, is actually hurting them more than it’s helping. THERE’S MORE TO NUTRITION THAN JUST WEIGHT LOSS.


So, let’s better apply this to our daily lives. Your metabolism can be broken down into 3 main categories. #1 is your Basal Metabolic Rate (BMR), this is the amount of calories your body needs in order to survive. Think about this like, if you just laid in bed all day and didn’t move at all, you’d burn “X” amount of calories, just because you’re alive. Your BMR is responsible for 60-70% of your total calories burned ALL DAY, and it’s a lot more than people realize, which is another reason why the starvation diets, aren’t feasible long term for overall health. Click here if you want to calculate yours, it’s an estimate but still good to know. *Something to consider is, the more muscle you have, and the denser your bones, the more calories you will burn in order to maintain it. Another reason why lifting weights is so important, especially as we age. Click here if you want to calculate yours, it’s an estimate but still good to know. #2 is actual physical activity. How much you walk, move around, fidget at work, lifting weights, doing cardio, etc all play a factor in this, yet its only 30-40% of your total calories burned (depending on the person and their activity level). Lastly, #3 is the Thermic Effect of Food. This is how many calories your body uses to digest the food you eat. Protein is the most thermogenic, which is one of the reasons I recommend high protein diets, but since this only accounts for 10% of total daily calories, there are often more important factors to look for first. These 3 combine to form your Total Daily Energy Expenditure (TDEE), this is the number you are looking to measure when either losing or gaining weight. If you eat more than your TDEE, you’ll gain weight. If you eat less than your TDEE, you’ll lose weight.


Now that the biology lesson is done, let me tell you, your metabolism doesn’t start slowing down until around age 60 in women, and 70 in men [2]. Our metabolisms seem to remain stagnant from age 20-60, then slowly decline, but only by around 50-70 calories per day [3]. But, what does decline in our 20s is our physical activity. Almost like clockwork, studies show that [4] physical activity DROPS with age (the drop is much more drastic for men). If physical activity drops, that’s 30-40% of the calories you burn per day, meaning a lot less calories you’re burning each and every day, over years and years, it adds up.


BUT this should be very encouraging, this doesn’t mean you have a broken or slow metabolism, it just means you’re an adult and have a little bit more responsibilities now, and might even have a job that requires you sit all day. You might not be on a sports team anymore that keeps you in shape after sitting in class all day, like back in high school. Also, being an adult means that if you wanna eat an entire cake all by yourself or eat McDonalds every day, technically, no one can stop you. So, we tend to eat a little more, or the quality of food we eat is a little less than when our parents would cook for us.


Morale of the story, you control this. You control how much you move. You control if you lift weights and get stronger. You control what you eat. No more blaming the metabolism. Your metabolism can be broken or slow or fast. People with “fast” metabolisms, tend to literally just move more and are normally more active in general. So go out there and have a fast metabolism.

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