"If you really feel like you're doing everything right and not seeing progress, it's worth looking at where you're getting your food from and what's being sprayed on your food," says Slayton. Some of the chemicals in plastics and pesticides are endocrine disruptors called obesogens, which can set you up for weight gain.
It's not just unpleasant to be anxiety-ridden—it's also bad for your metabolism: "Cortisol's a big stress hormone, and when that's activated, your body's more likely to be in fat-storage mode," says Slayton.
People who are sleep-deprived on a regular basis tend to weigh more than those who get a good night's rest most nights. Why? Research shows it can throw the hormones that control appetite out of whack, making you hungrier and causing you to eat more. Slayton recommends logging at least seven hours a night.
Caffeine gets a bad rap, but it can actually give your calorie burn a slight boost, says Slayton. No one's suggesting you start pounding the stuff, but if you're already drinking green tea or coffee most days, keeping it a part of your routine could help your metabolism run at top speed.
There's a lot of emphasis on how important it is to eat regularly so as not to slow your metabolism down, but there's also research that suggests going several hours without eating could be better for you, metabolically speaking. "What I usually suggest for clients is a period of 12 hours without food," says Slayton. "You're hurting your metabolism if you're having a midnight snack and a breakfast before your workout at 7 a.m."
You know that exercise is crucial for keeping your metabolism fired up, but if you swear by running or indoor cycling—and only running or indoor cycling—you're not building the lean muscle that'll really give your metabolism a boost, says Slayton. Start incorporating strength training into your workouts to up your calorie burn even more.
When you're low in vitamin D, you lose weight slower and your levels of the hormone ghrelin, which makes you hungry, are higher," says Slayton. Since it can be difficult to get enough vitamin D from your diet, she recommends taking a supplement from November through March—when you won't be getting as much of the nutrient from sunlight—to help you drop pounds more easily.
"Your body needs fluids to perform all of the functions it needs to," says Slayton. And when it's not performing those functions as well, it's not burning as many calories. Something else to keep in mind: A lot of the calorie burn from drinking water comes from your body working to bring cold water to 98.6 degrees—so drinking hot water with lemon or hot tea all the time won't be as good at boosting your metabolism as cold water will.