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.
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.
Healthy fats such as avocados, coconut oil, extra virgin olive oil, avocado oil, and ghee have a number of benefits. These include reducing the risk of heart attack, coronary artery disease, high cholesterol, high blood pressure, cancer, diabetes, and metabolic syndrome.23,24,25,26,27 They can keep you satisfied longer, reducing the risk of overeating and snacking. Healthy eating doesn’t mean deprivation! Healthy fats taste good and improve your brain health, and so may help you feel emotionally satisfied, lowering the risk of emotional eating.28
Now that the whole sober curious moment is making not drinking trendy, it’s easier to find alcohol-free options. Less alcohol not only means you’re drinking fewer calories, it can also mean fewer late-night bowls of ramen or plates of double cheeseburgers on the way home from happy hour. Today, it’s also easier to maintain a social life when you’re not overdrinking, since there’s the new perception that you’re not saying no to a beer or five; you’re part of a “movement.”
Eating well isn’t just about skipping out on processed junk food. It’s also about filling up your plate with clean, healthy foods that can actually assist in your weight loss. Healthy fats like those found in olive oil, avocados and nut butters nourish your body while helping you feel full longer—which means you’re less likely to overeat. Incorporating healthy sources of protein like eggs and salmon will also help you feel more satiated as well as fuel the muscles you’re building through that regular strength training we mentioned above! Hungry during the day? Keep a small pack of heatlhy almonds or other nuts in your bag to snack on in a pinch.  Just a handful will keep you satisfied until your next meal, all while providing healthy protein, fat and fiber. Don’t wait until you’re tummy is growling! Be prepared.
As you enter your forties, you are also entering perimenopause, when levels of your sex hormones progesterone and estrogen decline. Besides regulating your menstrual cycle and reproductive functions, these hormones also impact restful sleep and relaxation. A decrease in progesterone and estrogen levels may lead to sleep disturbances, restlessness, and insomnia.1 Because changes in sleep patterns have been associated with weight gain, sleepless nights may make weight loss increasingly difficult.2
Your body has to work harder (meaning it burns more calories) digesting protein than it does fat or carbs, so Palinski-Wade recommends the strategy of upping protein intake to many of her clients, including women who are 40 and over. "Although I don’t promote very high-protein diets, increasing your protein intake from 15 percent of your total calories to 30 percent can help you boost the calories your body burns during digestion, which may just help speed weight loss."
Even if you’re eating reasonably well, you can still be in a calorie surplus. Whether you’re eating oversized portions, taking mindless bites while prepping family meals or grazing as part of a new work-from-home norm, all that noshing adds up. Tracking your food intake can be helpful. In one 24-week study, researchers found that time spent logging food intake was significantly linked to weight loss. If tracking your food (even with an app) sounds daunting, consider that by the end of the study, those who were still committed to tracking spent just 15 minutes a day doing it — about what you might spend scrolling through Facebook or Instagram.
One of the main culprits for weight gain is, of course, our hormones, which start to change right around the mid-30s and into the 40s. This change in hormones, less estrogen for women and less testosterone for men, cause the fat in our bodies fat to shift to the middle of the body while abandoning other areas of the body you could care less about. That's one reason you may get a little fluffier around the middle while other parts of you actually get smaller.
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