Starting in your 30s, you can lose three to five percent of your muscle mass each decade if you don’t stay active. Note the last part of that point: “If you don’t stay active.” As you get older, "there's a lot of competition for your time and energy," says Dr. Yancy. For some men, that can push exercise out of the picture. But it doesn't take heroic efforts to put it back into your life.
When you’re under-rested, your appetite-regulating hormones get short-circuited, so your appetite goes into overdrive, but the hormones that tell you you’re full don’t kick in promptly. Studies also suggest that when you’re sleep-deprived, it alters the way you think about food, so you have stronger cravings for sweets and other less healthful eats.
Changes in your activity levels are one of the main reasons that losing weight after 40 may be more challenging than before. Like many women, you may be putting others first and simply not finding time to exercise. You may also notice that your joints can no longer handle the same activities as before. However, a lack of exercise can lead to muscle loss and fat gain.
Your metabolic rate naturally continues to decline 5 percent each decade once you hit 40.3 Your resting metabolic rate (RMR) determines how many calories you just to survive. It is determined by a variety of chemical reactions inside your body. These reactions rely on your mitochondrial function and sodium-potassium pumps. Your mitochondria help to create energy, while your sodium-potassium pumps generate muscle contractions and nerve impulses.4,5,6,7,8 Both of these processes become less effective over the years and slow your metabolism.9,10 If you eat more than your RMR yet lead a sedentary life, you set yourself up for weight gain.
As you reach mid-life, the pressures pile up. Just think of the typical stressors, like caring for kids and aging parents, facing financial burdens and dealing with the demands of a job. When you’re experiencing stress, your body responds by releasing the hormone cortisol. If your stress diminishes, your hormone levels return to normal, but if you’re experiencing ongoing stress from “adulting,” cortisol levels will remain high. This can set off a series of biological events that may lead to an increased appetite with more cravings and a propensity to store fat in your belly.
"One of the reasons that it's difficult to lose weight in your 40s is that you are beginning to lose muscle mass, so the composition of your body tissue changes," explains Keri Peterson, MD, Women's Health advisor. "Having higher muscle mass raises your metabolism, so your body burns more calories." So when you're dealing with the opposite—less muscle mass—that means a slower metabolism. Argh.
Hormone imbalance can also wreak havoc on your weight. Keep in mind that perimenopause and other hormone changes can start when you are in your 40s. Estrogen dominance will definitely interrupt weight loss but so will the imbalance of cortisol, leptin and insulin. We have a great article that covers, in great detail, how these hormones affect your body. Check out Balance These 4 Hormones If You Want To Lose Weight for more information!
When you were young, you probably didn't spend too much time thinking about preparing your body for the future. In your teens and twenties, you're in peak condition and it's the perfect time to start exercising. Cut to 20 years later and, if you didn't start exercising, you probably wish you had since there's something we all start to experience in our 40's—weight gain.