by Lily Grace
t seems to be a given. Everyone says it: “As you age, your metabolism slows down.” Darn it! Now it’s even harder to lose weight.
But why? Well, we’ve taken a look at the science and explain it below. So, before you sit down with another bowl of ice cream, consider reading this.
In your 20s
Most women enjoy their highest basal metabolic rate in their late teens or early 20s, say most doctors. Some women will hit it a bit earlier, others later, which has a lot to do with genetics, but your activity level also plays a big role. After all, the more you run across campus or hit the gym, the more muscle you’ll build and the higher your metabolism will be. Plus, until you’re about 25 or so, your body is still building bone, and that process burns up calories.
However, it doesn’t last that long. According to the American Council on Exercise, your basal metabolic rate drops roughly 1-2% per decade. Generally, by their late 20s, many women notice that they can’t eat the same things they used to without gaining weight and that the weight doesn’t fall off as easily as it once did. Since this drop starts right about the time people settle into the (largely sedentary) workforce—and start losing muscle—an office job might be partially to blame.
In your 30s
As you lose muscle, your natural calorie-burning ability slows even more. And as you lose muscle and gain fat, fat can develop into the muscle and cause weight gain and metabolic dysfunction. Plus, during your 30s, you aren’t producing as much human growth hormone as before, which also leads to a dip in your metabolic rate. However, strength training can help you build muscle and produce more human growth hormone, both of which keep your metabolism running as fast as (or faster than) it did when you were 20.
And then for women, there’s the pregnancy factor. A huge calorie burn comes from breastfeeding (should they choose to do so). The average woman who breastfeeding full time can expect to burn an extra 500 to 1,000 calories per day. Unfortunately, as soon as you start weaning your little one, your metabolism goes back to pre-pregnancy levels—as long as you haven’t lost any muscle since you got pregnant.
In your 40s
Women can say goodbye to your hormones. Around 40, levels of estrogen, progesterone, and (again) human growth hormone decrease. And metabolism follows suit. That means you’ll have to focus on reducing your caloric intake during your 40s in order to maintain your weight. If you’re working out, that might only amount to eating about 150 less calories per day. But if you don’t exercise and sit most of the day, you’ll probably have to cut more calories to stay svelte.
Also by 40, your body’s natural decline in muscle mass, called sarcopenia, sets in. To combat the loss of lean mass and keep your metabolism revved, you really have to turn to strength training. According to research from the Harvard School of Public Health, people who lift weights put on less belly fat as they age than cardio bunnies. While any exercise will help you burn calories while you’re at the gym, strength training gives your metabolism the biggest boost after your workout ends. Eating the right amount of protein (about 100 to 120 grams a day) will boost your efforts to get stronger.