If you’ve ever had trouble losing weight, you’ve probably placed at least some of the blame on a slow metabolism. It’s true that your basal metabolic rate — the rate at which your body uses energy — can affect your ability to shed pounds. But there are also a few external, controllable factors that can slow down that metabolic rate, says Michael West, MD, an endocrinologist with Washington Endocrine Clinic in Washington, D.C.

Here are eight triggers that can slow metabolism, some (but not all) of which you can control, to make sure you aren’t sabotaging your weight-loss efforts.

1. Age. As you get older, your ability to quickly use up energy diminishes and your metabolism can slow. “As cells age, they do metabolize less rapidly,” Dr. West says. Older people also tend to have less muscle mass than younger people, which translates to a reduced metabolic rate. While you can’t make yourself younger to speed up your metabolism, West suggests being diligent about getting enough exercise — many people tend to get out of the habit as they age. The Centers for Disease Control and Prevention suggests that adults 65 and older get two and a half hours of moderate-intensity aerobic activity every week and do strengthening exercises on all the body’s major muscle groups at least twice a week.

2. Stress. When your nerves are frazzled, your body releases cortisol, a hormone produced by the adrenal system that is linked to weight gain. “There are definitely established links between psychological stress and the adrenal system,” West says. To make sure that stress isn’t making it harder to take off pounds, try to calm yourself by reducing the controllable stressors in your life. For example, if heavy traffic makes you nervous, avoid the roadways during rush hour. Regular physical activity, deep breathing, and even professional help from a psychologist or counselor may also be helpful.

3. Poor sleep habits. Getting too little shut-eye can significantly alter your body’s processes enough to predispose you to gain weight. “There was a recent study where healthy volunteers were subjected to poor sleep,” West says. “Even over one night, the lack of sleep was significant enough to disrupt their metabolic patterns and give them more insulin resistance, which is a risk factor for diabetes.” Insulin resistance has also been associated with obesity. To increase the chances of boosting metabolism, adults should get seven to nine hours of sleep each night.

4. Lack of exercise. Exercise not only helps you expend more calories while you’re physically active, but there’s also some evidence that it may increase your resting metabolic rate. To make sure you get enough exercise for boosting metabolism, set aside a dedicated period of time, rather than trying to accomplish it during the course of your everyday activities. Adults ages 18 to 64 need about two and a half hours of moderate-intensity aerobic activity each week, as well as strengthening exercises for all muscle groups twice a week.