Good mood, better metabolism

These two seemingly disparate things are connected in surprising ways, new science reveals. And boosting one will help kick the other up a notch. Here’s how it works.

Portrait of Tammy Strobel

These two seemingly disparate things are connected in surprising ways, new science reveals. And boosting one will help kick the other up a notch. Here’s how it works. 


A fast metabolism, a happy outlook – these are two things we can all agree are worth chasing. And now, scientists are realising 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, 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, an associate professor of nutrition at the University of Montreal. That’s when one’s mood starts to rise. 

The following five strategies will help deliver a happy mind-body balance. 

Exercise early 

Working out, especially running and cycling, causes your leptin levels to fall, triggering a surge of dopamine, Stephanie 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.” 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 up your metabolism even more. 

Pump up 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 3.2 times higher leptin levels than others, 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 18mg of iron a day. 

Find your funny 

Your body responds to laughter the same way it does to a short bout of moderate exercise, researchers from Loma Linda University in California  discovered. They found that people’s leptin levels decreased after watching a comedy film. 

A study from Vanderbilt University  found that genuine laughter increases your metabolism by up to 20 per cent, and there’s plenty of evidence that it makes you happier. The trick is to laugh every 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 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 Stephanie. Visceral fat also cranks out leptin and may increase your odds of leptin resistance. 

Sleep deeper 

It’s no secret that a lack of zzzzs makes you cranky, but losing just two hours of sleep for three days can also cause your metabolism to grind to a halt, according to a 2015 study. Sleep deprivation increases your cravings for junk food, Stephanie 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, and worsens one’s mood.” 

It’s not just how much you snooze but how restorative those hours are, too. Sleep interruptions are worse for your mental state than not logging enough shut-eye, the journal Sleep reports. Invest in blackout curtains and a white-noise machine, and dim the brightness of your phone to tone down the sleep-sapping blue light.