A fast metabolism, a happy outlook — these are two things we can all agree are worth chasing. And now, scientists are realizing that going after one may naturally deliver both.
What we know for sure: The key to this connection is the hunger hormone leptin, which tells your brain that you feel full. “Leptin impacts not only your food intake but your mood as well,” says Paul Burghardt, Ph.D., an assistant professor of nutrition and food science at Wayne State University in Detroit.
This is partly because of the hormone’s relationship with dopamine, a neurotransmitter that controls happiness and motivation. Generally, when leptin levels dip, the release of dopamine increases, says Stephanie Fulton, Ph.D., an associate professor of nutrition at the University of Montreal. That’s when mood starts to rise.
Try the following strategies to help reach a happy mind-body balance.
Exercise early in the day
Working out, especially running and cycling, causes your leptin levels to fall, triggering a surge of dopamine, Fulton says. “When leptin declines, it sends a signal to your body that you need to eat. That stimulates dopamine production, which in turn increases your motivation to exercise longer,” Fulton explains. This response is a holdover from prehistoric times. Back then, our drive and outlook were boosted whenever hunger kicked in to set us up for success in finding food. To take full advantage of this effect, hit the road or the gym in the morning, before breakfast. Since you haven’t eaten for hours, your leptin levels will already be low, and you’ll be able to go longer, which may rev your metabolism even more.
Pump up on iron
If you’re deficient in this mineral, you’ll be less likely to score the perks of the leptin-dopamine response. People with the lowest amounts of iron had triple the leptin levels of those with high iron, reports the Journal of Clinical Investigation. This could even lead to leptin resistance, which occurs when leptin levels remain too high for too long; the hormone stops affecting your brain, contributing to weight gain and moodiness. Aim for about 18 mg of iron a day.
Eat better fats
Replacing saturated fat from meat and dairy with polyunsaturated and monounsaturated fats (in salmon, avocados and nuts) may benefit your metabolism and your mood, research in the journal Frontiers in Neuroscience reveals. Saturated fats make you accumulate visceral fat, which slows the metabolism and produces inflammatory molecules that are linked to depression, says Fulton. Visceral fat also cranks out leptin and may increase your odds of leptin resistance.
Do what it takes to get a good night’s sleep
It’s no secret that a lack of zzz’s makes you cranky, but losing just two hours of sleep for three days can also cause your metabolism to slow. Sleep deprivation increases your cravings for junk food, Fulton adds. “It’s a cycle. You don’t sleep well, so you’re more stressed and crave comfort food that’s high in saturated fats. This increases inflammation, worsening mood.”
Invest in blackout curtains and a white-noise machine, and dim the brightness of your phone to tone down the sleep-sapping blue light.
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Erin O’Donnell is a freelance health and science writer, parent, and graduate of Northwestern’s Medill School of Journalism. Walks by Lake Michigan make her happy.