At this very moment, your body is crackling and sparking with the chemical reactions that make up your metabolism. The calories you’ve consumed are being converted to the energy that will be used to power all the systems in your body: breathing, circulating blood, digesting food, growing and repairing cells, managing hormone levels, regulating body temperature, etc.
Your basal (resting) metabolic rate is the minimum number of calories your body needs to perform these functions while you’re at rest. This rate varies from person to person, and is influenced by a number of factors, including age, sex, diet, activity level, sleep, thyroid health, injury or disease, and body composition.
Age: As we age, our metabolism moves through four phases:
- From birth to 1 year old, metabolism is very high (approximately 50 percent above normal adult metabolism).
- From age 1 to 20, metabolism slowly declines.
- From age 20 to 60, metabolism levels out.
- From age 60 onward, metabolism declines. This decline can be reduced, however, by working to maintain muscle mass.
Sex & Body Composition: Men and women have different body compositions and, therefore, differing metabolic rates. In general, men have more muscle mass, and women have more adipose (fat) tissue. Lean muscle tissue is more metabolically active than adipose tissue.
Diet: Eating too little food causes the body to shift into “famine mode,” and slows down the basal metabolic rate.
Activity Level: Moving around burns more calories than resting. Activities that build muscle mass increase our metabolic rate while we’re doing them, and then keep that rate higher—even when we’re sedentary.
Sleep: Sleep deprivation can decrease resting metabolic rate. Being well rested can help bump that rate back up to normal.
Thyroid Health: The thyroid is a gland that produces hormones that impact basal metabolic rate. If too little or too much thyroid hormone is being produced, the rate becomes unbalanced.
Injury or Disease: Healing takes energy! Basal metabolic rates increase when recovering from injury, disease, or surgery. Proper nutrition fuels these increased needs.
Feed the Fire
While your basal metabolic rate is considerably influenced by genetics, there are things you can do to help keep your metabolism burning well:
Build More Muscle: All physical activity increases metabolism while you’re doing it, and high-intensity training can keep it revved-up for hours afterwards. But to keep the metabolic fires burning brighter 24 hours a day, look to resistance/weight training. This type of exercise builds the muscles that constantly burn fuel, and it works for men and women, the young and the old. It’s never too late to begin weight training. Research has shown that even frail people over the age of 75 can build muscle mass. Weight/resistance training can be done at a gym using machines, or at home using dumbbells, resistance bands, or bodyweight exercises. It’s always a good idea to check with your healthcare provider before beginning a new exercise routine. Then, look for the sweet spot: a weight that’s heavy enough to be challenging, but light enough that you’re able to use proper form. Do those exercises two to three times a week, and before you know it, you will have begun to shift your body composition towards being stronger and more metabolically active. For information about how to get started building muscle, check out the Northern Wilds article Pump It Up! from January 2023.
Get Enough Rest: Slow down to speed up! Everyone has the occasional rough night, but if you’re regularly sleep deprived it can slow down your basal metabolism. Focus on getting your sleep back on track, and that will help get your metabolism back on track as well.
Eat Enough Food: As far as your body is concerned, low-calorie diets and famine are the same experience. When your food intake is severely reduced, your body lowers its metabolic rate. This conserves “fuel” so that you’ll be able to withstand what it perceives as starvation. Make sure you’re getting enough high-quality calories (like vegetables, fruit, whole grains, lean protein, and healthy fats) to fuel your fire.
Remember, if you’re experiencing fatigue, weight loss, or weight gain that seems unexplained, call your healthcare provider. These can be signs of health conditions that need prompt care.
The chemistry that makes up your metabolism is complicated. But luckily, taking care of your metabolism is straightforward: move around, eat well, build strength, and rest up. Keeping the fires inside glowing will help you keep going!
