It seems as we age we hear the term “Metabolism” thrown around a lot. It’s a known fact that after age 30 our Metabolic Rate or the rate at which our bodies takes in nutrients and burns calories begins to slow down at a rate of 1-2 percent per decade beginning around age 20! *For the purposes of this post, I will be using the terms “metabolism” and “metabolic rate” interchangeably.
According to Natalie Digate Muth, MD, MPH, RD, “the decline in metabolism is relatively slow and steady, at about 1 to 2 percent per decade. That means that at age 30, you’d have to eat about 150 fewer calories per day to weigh what you did at age 20.” 150 fewer calories per day may not seem like much, but it’s a time when many women are in the throes of their careers, getting married, or raising children. Exercise may not be as consistent, diet choices may not be as healthy and the combination of lack of sleep or job/family related stress can mean unwanted weight gain.
Once men reach the age of 40 and women reach the age of 50 the decline of their metabolic rate or “Metabolism” often accelerates.
A decreasing metabolism does not mean you are destined to be overweight, however. In fact that are steps you can take to prevent middle-aged weight gain. But before we discuss exactly what we can do to countereffect a naturally occurring process, let’s first discuss what metabolism is.
So what is Metabolism?
Metabolism
Technically speaking, Metabolism is the word used to describe all of the biochemical reactions in your body. It’s how your body takes in nutrients and oxygen and uses them to fuel everything you do.
Your body has an amazing capacity to grow, heal, and function 24 hours a day, seven days a week. What’s even more amazing is that even when you don’t eat healthy, your body works tirelessly to function optimally. And while given enough time your unhealthy habits will eventually catch up with you, if provided with the right amount of exercise and good nutrition, you can actually stave off the negative effects of a decreasing metabolism.
In a nutshell Metabolism:
● Allows activities you can control (e.g. physical activity)
● Allows activities you can’t control (e.g. heart beat, wound healing, processing of nutrients & toxins, etc.)
● Allows storage of excess energy for later*
All of these processes when added together affect that rate at which you burn “energy” or calories.
Contrary to popular misconception, a “calorie” is a unit of heat or the amount of energy it takes to raise a thermometer one degree NOT a fat cell. Calories don’t make fat, unless you eat more of them than your body needs to function.*
Which brings us to the “metabolic rate”.
Metabolic rate
This is how fast your metabolism works and is measured in calories.
The calories you eat can go to one of three places:
● Work (i.e. exercise and other activity).
● Heat (i.e. from all those biochemical reactions).
● Storage (i.e. extra leftover “unburned” calories stored as fat).
As you can imagine the more calories you burn as “work” or “creating heat” the easier it is to lose weight and keep it off because there will be fewer “leftover” calories to store for later.
So what affects your metabolism?
- Thyroid: This gland at the front of your throat helps coordinate and regulate energy used by your body. It releases hormones to tell your body to “speed up” or “slow down” your metabolism. The more thyroid hormone there is, the faster things will work and the more calories you’ll burn which is why people with too much (hyperthyroid) are often very thin and people with too little (hypothyroid) struggle with weight loss.
- Size: How big you are matters too! Larger people tend to have higher metabolic rates, because their bodies require more calories to function, but your body composition is crucial too!
- Muscles Mass: Muscles that actively move and do work need more energy than fat does. So the more lean muscle mass you have (i.e., the more muscle you have compared to fat), the more energy your body will burn and the higher your metabolic rate [metabolism] will be. Even when you’re not working out!
This is exactly why weight training is often recommended as a part of a weight loss program and why lifting weights as we age is the “Holy Grail” of weight loss–even more so than cardio alone. If you want to stay fit and trim throughout the aging process, you have to lift weights, because lifting weights make muscles grow and muscles use calories.
- Age: Have you ever commented to someone younger than you that they’d better enjoy that _________(insert food name here) while they can? Or lament about when you were younger and could skip a few meals and lose “5” or “10” pounds? While growing requires EXTRA calories, calories from processed foods and snacks should not be a growing child’s primary source.
- Weight loss: can affect your metabolism as well. When people lose weight too quickly either by crash dieting or excessive exercising, their metabolism often slows down.
- Aerobic exercise: Also known as Cardiovascular exercise (the term “cardiovascular” refers to working out the heart muscle) temporarily increases your metabolic rate. Your muscles are burning fuel to move so they’re doing “work”, but unlike muscles, which burn fuel even at rest, once you stop performing cardio, your metabolic rate slows back down as well.
- Food: The type of food you eat also affects your metabolic rate! Your body actually burns calories to absorb, digest, and metabolize your food. This is called the “thermic effect of food” (TEF).
You can use it to your advantage when you understand how your body metabolizes foods differently.
Fats, for example, increase your TEF by 0-3%; Carbs increase it by 5-10%, and Protein increases it by 15-30%. By trading some of your fat or carbs for lean protein you can slightly increase your metabolic rate.
Another bonus of protein is that your muscles need it to grow. By working them out and feeding them what they need, they will help you to lose weight and keep it off.
And don’t forget the mind-body connection. There is plenty of research that shows the influence that things like stress and sleep have on the metabolic rate.
So what habits can you practice to keep your metabolism running optimally throughout your lifetime?
- Lift weights: Remember, muscles are “metabolically active”–they take calories (aka “energy”) to grow.
- Move more: As we age, there is a tendency to become less and less active. The more you can move, whether it’s running, biking, swimming, jogging, the better able we are to maintain a healthy weight, control blood pressure and diabetes and keep our metabolism humming.
- Eat healthy: As we get older, we require less quantity and more quality! Whole, fresh, unprocessed food is not only better for you, it can make you look and feel better too!
- Get more sleep: Studies indicate that when we sleep more we eat less, due to two key hormones which regulate hunger. Lack of sleep also causes your body to produce Cortisol and when you produce more cortisol you store more fat!
References:
How much does your metabolism really slow over the years?
Regular exercise and the age-related decline in resting metabolic rate in women