Even if stressful situations don’t cause you to binge on fatty foods, your body may take longer to process any calories that you do eat. In a 2014 study from Ohio State University, women who reported being stressed out over a 24-hour span burned, on average, 104 fewer calories after they ate a meal of eggs, sausage and biscuits. The researchers point out that over the course of a year, this deficit could translate to an 11-pound weight gain.

“The stress response activates the hormone cortisol” explains Celi, “which has been clearly associated with a worsening of metabolism and, in the long-run, increasing the risk for obesity.” In other words, to help speed up metabolism make sure to wind down more often.

Not getting enough quality shuteye has also been shown to slow metabolism in both men and women; this also may have to do with the brain’s secretion of cortisol when the body is under stress, says Celi. And even if you hit the hay early, that may not be enough. Research has shown that broken sleep (when you’re woken up frequently throughout the night) isn’t nearly as restorative as seven consecutive hours. So on top of crawling under the covers early, be sure to give yourself enough hours to get the rest and recovery your body needs.

Not only does muscle weigh more than fat, but it uses more energy, too. The average woman in her 30s who strength-trains 30 to 40 minutes twice a week for four months will increase her resting metabolism by 100 calories a day. That means you're resetting your thermostat to keep running at that rate even on the days when you don't make it to the gym, Hunter explains.

Sleeping in a cool room seems to increase people’s percentages of brown fat — a type of fat that acts more like muscle — according to a 2014 study conducted by Celi and colleagues at the National Institutes of Health. The research involved five male volunteers, who slept in climate-controlled rooms with only light pajamas and bedsheets, for several months. After four weeks of 66-degree nights, they’d nearly doubled their amounts of brown fat, and also experience an increase in their calorie burn.

“It would be extremely naive to do this and expect to lose weight to the extent you would on a diet,” Celi says. “On the other hand, we did see a measurable increase in glucose metabolism that could certainly add up over time.”

Keeping your home or office cool during the day may also have a similar effect, he adds.

A few small studies have shown an association between caffeine consumption, increased metabolic burn, and a reduced risk for type 2 diabetes. Celi says this could possibly be because it helps the body break down fat.

But don’t go overboard: Too many caffeinated beverages a day can cause nervousness, nausea or insomnia. Plus, some coffee beverages are high in fat and sugar.

You’ve heard they're bad for you. But trans fats also slow down your body's ability to burn fat. "They have an altered shape and make your biochemistry run funny," Hyman says, explaining that trans fat binds to fat and liver cells and slows metabolism. Eating trans fat can also lead to insulin resistance and inflammation, both of which cripple metabolism and can cause weight gain.