During your 30s, levels of key muscle-building hormones, including growth hormone and testosterone, begin to decline. As a result, you may start losing muscle, which can slow your metabolism and lead to weight gain.

Try this: Pile on the protein. "My research has found that eating more protein, especially between meals and after exercise, can build muscle mass, helping reverse the decline in metabolism,"says Caroline Apovian, MD, an endocrinologist and professor of medicine at Boston University Medical School. She recommends getting up to one and a half grams per kilogram of body weight daily (so about 95 grams for a 140-pound woman). And you may build more muscle if you spread your protein intake evenly throughout the day. In a small 2014 University of Texas Medical Branch study, healthy adults who ate around 30 grams of protein at each meal had 25 percent better mixed muscle protein fractional synthesis, a key component of muscle building, after 24 hours than those who got most of their protein (63 grams) at dinner. If your diet looks like the latter group's (11 grams at breakfast, 16 at lunch), you can help equalize your intake by adding two eggs and a cup of yogurt to breakfast and a glass of milk and a handful of nuts to lunch, then scaling back dinner proteins to half the usual amount.

The Bone Zone
This decade is a good time to protect the bone you banked in your 20s so it will still be with you after menopause, when a sharp drop in levels of the reproductive hormone estrogen often leads to a swift decline in bone mass. "In your 30s, it becomes a matter of maintaining bone density,"says Erika Villanueva, MD, an endocrinologist at New York University Medical Center. "Your bones will never be stronger than they are now." While researchers aren't exactly sure how estrogen helps maintain bone density, one State University of New York at Buffalo lab study found that it stops the activation of enzymes that kill off osteoblasts, the cells responsible for bone formation.

Healthy habit: To keep bones strong for the future, sip tea, which is rich in flavonoids—phytochemicals that may help reduce bone loss. A 2015 Australian study found that women who drank at least three cups of nonherbal tea per day had a 30 percent lower risk of experiencing an osteoporosis-related fracture than women who rarely sampled the brew. Another bone-friendly practice: cooking with olive oil. Some research suggests that oleuropein, a compound found in virgin olive oil, may help prevent bone loss by enhancing the formation of osteoblasts.

Good to know: A diet rich in flavonoid-packed foods—like apples, strawberries, and grapes—is associated with less weight gain over time, according to a new study in BMJ.

Learn how to manage your changing hormones in your 40s and 50s too.


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