Reason 1: Haywire Hormones
Poor diet, bad genes and just getting older put you at risk for insulin resistance, a condition in which the body can't easily absorb glucose from the bloodstream, causing the liver to store it as fat. It's estimated to impact one in four people in Western countries. Extra fat stirs up even more trouble by acting like little estrogen- making laboratories, says board-certified gynecologist Sara Gottfried, MD, author of . "Estrogen makes you deposit more fat. That fat then produces more estrogen, turning you into a perpetual weight-gain machine." Hormones in meat compound the problem, as do exposure to pesticides, plastics and industrial chemicals, all of which mimic estrogen.
"Whether it's 5 pounds or 50, exercise and eating less won't cut it if your hormones are off," Gottfried says. She suggests asking your MD for a fasting blood sugar test, which can detect insulin resistance. (A level of 70 to 85 mg/dl is ideal, notes Gottfried.) Failed your test? Time to "reset" your levels. Start by reducing sugars and starchy carbs to avoid blood sugar spikes that lead to fat storage. Also up your fiber intake to between 35 and 45 grams a day. It helps flush estrogen out of your system. Skipping your nightly vino might help too, as booze impacts hormones. For every alcoholic beverage consumed, the average amount of circulating estrogen in your body increases by about 6%.
Reason 2: Missing Magnesium
This critical mineral is required for the chemical reactions that allow your body to turn food into energy. When you don't get enough, you're missing an essential nutrient that helps you burn fuel efficiently. But three out of four Americans don't get enough magnesium, which is reflective of a poor overall diet, says Drew Ramsey, MD, author of the forthcoming . "The mineral is found mainly in plant-based foods and leafy greens, so if you're low in magnesium, you're probably relying on highly processed or sugary foods."
Carolyn Dean MD, ND, author of , recommends that women ages 30 to 50 pay special attention to their intake of magnesium, which has a recommended daily allowance of 320 mg. Try incorporating more magnesium-rich foods, such as spinach, beans, whole grains, chia seeds and nuts, into your diet. Bonus: Diets with higher levels of magnesium are associated with stronger bones and lower diabetes risk.
Reason 3: Divergent DNA
You and a friend make a pact to cut out sweets for a week. She drops 5 pounds; your scale seems stuck. Why? Could be your genes. Last year, researchers found evidence that individuals with certain physiologies lose less than others when limiting calories. Recent research also supports the theory that variations in genes might predispose some people to belly fat.
With that in mind, companies like and claim to test your DNA for genetic variations related to fat storage and more, then use their findings to customize a diet and exercise plan. But experts say it's too early to connect the dots between genes and a diet that will make you lose weight. What's more, your DNA shouldn't shoulder all the blame. "While there are examples of individuals with genetically predetermined obesity, this represents a small percentage of obese people," says Ramsey. "Our genes set the foundation for our health, but everyone has the capacity to lose."
As you refocus your efforts, keep this in mind: "Your biology is not your destiny," says NIH research nutritionist Susanne Votruba, PhD, RD, who co-authored the aforementioned study. "It might take some people longer to slim down. Instead of comparing yourself to others, recalibrate your expectations."
Reason 4: Imbalanced Belly Bacteria
Deep within your stomach lives an ecosystem of trillions of bacteria called your gut microbiome. It's responsible for everything from extracting nutrients from food to protecting you from foreign invaders intent on making you sick. When "good" bacteria dominate, our GI system and immunity thrive. When "bad" bacteria grow in number, we get sick more easily.
"Increasing evidence shows that what you feed your gut microbiome can impact your weight," says Gerard E. Mullin, MD, an associate professor of medicine in and author of . "Sugary, fatty, processed foods and artificial sweeteners cause certain bacterial strains—which many doctors now refer to as 'fat-forming bugs'—to predominate and alter metabolism." These bad gut bugs may also increase inflammation, promote fat storage and spur insulin resistance. But fermented foods, like yogurt, kefir, kimchi and miso soup, are probiotics that create "good," healthy communities of bacteria that promote leanness.
Tweak your diet to make your gut an inviting spot for weight-controlling bacteria by consuming both a daily serving of fermented food and eating prebiotic foods, a select group of high-fiber carbohydrates on which healthy bugs love to feast. Prebiotics like oats, beans, cruciferous veggies, berries, nuts and green tea "act like Miracle-Gro for the friendly bacteria in your microbiome," says Mullin.
Reason 5: Skimping on Sleep
Adults who turn in late on weeknights are more likely to gain pounds and have higher BMIs than their early-to-bed peers, according to a 2015 study. When you skimp on sleep, levels of the appetite- suppressing hormone leptin dip, while ghrelin (a hormone that stimulates hunger) rises. Brain scans show more activity in the pleasure-seeking areas of sleepy individuals' brains, meaning they have a harder time refusing junk food.
Gottfried suggests treating your metabolism like an iPhone: Without a full charge, it will slow down and eventually stop working. Turn in at whatever time necessary to let you log seven to eight hours, and make your bedroom a dark, peaceful place—think blackout curtains and cool temps (65 degrees is ideal, says ). Cut down on caffeine and alcohol—"both can hijack sleep," Gottfried says. And speaking of phones, keep them off or out of your bedroom; not only does the screen's blue light disrupt your circadian rhythms, but a 2015 University of Houston study suggests that the flame retardants used to cool electronic devices may cause fat cells to proliferate. (That's why chemical substances like pesticides, cigarette smoke and BPA are called obesogens.)
Reason 6: Working Out So You Can Eat Badly
You can't exercise away your poor diet choices—but that doesn't mean you should let your sneakers collect dust. "Exercise is critical for a healthy mind and heart, strong bones and more," explains Amy Luke, PhD, professor of public health sciences at Loyola University Chicago Stritch School of Medicine. "But an overwhelming amount of literature suggests that very few people are able to burn enough calories through fitness alone to lose weight."
Think about it: It takes 30 minutes on a treadmill just to work off a Grande 2% vanilla latte. Plus, physical activity can ramp up your appetite—or make you feel justified in rewarding your sweaty efforts with dessert.
Instead of trying to outrun your cravings, throw energy into reducing portions. "You need to cut about 500 calories a day if you want to lose a pound a week, and it's much easier to do that by making smart swaps, like replacing your bagel with two pieces of whole wheat toast," says Ilyse Schapiro, RD, co-author of . Also consider spaghetti squash or zucchini "noodles" instead of pasta, and sparkling water instead of soda. Easy exchanges may get you to a feel-great weight—without having to complete an Ironman triathlon.