With summer coming up and the weather turning warmer, many of us feel motivated to shed a few pounds. And if we're going to all that trouble to lose weight, we don't want it to come creeping back (as it often does). But with all the conflicting diet and fitness advice out there, how do we know what actually works? Luckily, weight loss is an active field of research, and there is some new thinking on the right way to lose weight and keep it off.
If you do only one thing, start by cutting calories
Good news for people who don’t love to exercise — cutting calories makes more difference, at least in the short term. (You’re not totally off the hook for exercise though.)
Turns out, what — and how much — we eat seems to play a bigger role in losing weight than how much we exercise. A 2014 study compared three types of weight-loss programs: exercise-only, diet-only, and combined (diet + exercise). Researchers found that in the short term (3 to 6 months), diet alone worked as well as diet + exercise. In the long term (12 to 18 months), diet + exercise pulled ahead. (Exercise alone didn’t work as well as the diet-exercise combo in the short or long term.)
So despite what you might see on reality TV shows, it seems that exercise by itself doesn’t shed pounds as well as a combination of diet changes and exercise. “Think of diet as the cornerstone,” says Paul Aveyard, a professor of behavioral medicine at the University of Oxford who co-authored the study, while “physical activity is an important add-on.”
It makes sense. When you burn calories, your endocrine system secretes appetite-boosting hormones so that you replace those lost energy stores. A 2012 analysis of more than a dozen studies found that people in exercise programs burned less energy than expected and increased the calories they ate. That’s right — when you exercise, you may end up eating more.
To keep weight off, build muscle too
But wait, you say — if exercise is important in the long term, how does it keep the weight off? The key is to hack your metabolism by building more muscle, which burns more calories even at rest. In a 2010 study, Rania Mekary, a researcher at the Harvard School of Public Health, found that women were less likely to regain lost weight if they exercised for a half hour or more each day. In another study of 10,500 men, she and her colleagues found that compared with moderate to vigorous aerobic exercise (cardio), increasing weight training by 20 minutes a day led to less weight gain in the waistline.
“Making weight training a part of the regimen is key,” Mekary says, since it maintains muscle mass. That said, relying on exercise alone to lose weight isn’t feasible. Even slim women would need to exercise more than three hours a day to prevent weight gain if they didn’t also change their diet, says Mekary.
Choose foods with fewer calories
Now that we know calories are key, let’s take a closer look. What makes up your diet matters, too. Nutritionally, a calorie of butter is just like a calorie of broccoli — but only “from a purely physics standpoint,” says Dale Schoeller, a professor emeritus of nutritional sciences at the University of Wisconsin, Madison. Human biology is a bit more complicated.
Calorie-dense foods — things with a lot of fat and little fiber like desserts and meat — contain more calories in a smaller volume (more than the same volume of fruit or vegetable, for example). That means when we eat things like ice cream and steak it’s easy to eat a lot more calories than we need. Trouble is, we’re wired to love these high-energy foods — they seem to trigger reward pathways in the brain that drive us to overindulge. In a 2010 study, participants kept eating potato chips, chocolate malt balls, and other so-called “palatable snack items” even after a huge lunch — an average of 300 calories’ worth.
Low-energy-dense foods — like things with a lot of water and fiber and not much fat such as fruits, vegetables, and whole grains — help us control the amount we eat. That’s why when we eat brown rice or apples we feel full with fewer calories and we’re less likely to pack on pounds. Indeed, a 2011 study found that when people ate more fruit, vegetables, and low-fat dairy, they were less likely to gain weight.
While cutting calories might sound easier than exercising more, eating less — and steering clear of junk food — is tough work. “We have a mental battery, and every day you use a little bit more of your battery’s energy to stop yourself from eating stuff your body is telling you to eat,” Aveyard says. “As it depletes over time, you give up the weight loss attempt.” That’s why we need exercise, he explains; it can make some wiggle room by creating a calorie deficit each day.
Top Four Tips for Losing Weight
Although the research on weight loss is vast — and sometimes conflicting — it does strongly hint at a few practical, evidence-based strategies to help you lose weight and keep it off. To recap:
1. Eating fewer calories is probably more important for short-term weight loss than exercise.
2. Load up on low-energy-dense foods like vegetables, fruit, low-fat dairy, lean meat, and whole grains to feel fuller on fewer calories.
3. Steer clear of high-energy-dense foods like cookies and chips. They pile on the calories yet leave you wanting more, even when you’re full. If eating dairy or meat, choose low-fat dairy and lean meat.
4. Clock in at least 30 minutes of physical activity every day for your health, and make weight training a regular part of your fitness routine to keep metabolism high and the pounds off.
Selected references:
Champagne, Catherine M., et al. Dietary intakes associated with successful weight loss and maintenance during the Weight Loss Maintenance Trial. Journal of the American Dietetic Association. December 2011. [Link]
Cook, CM and Schoeller DA. Physical activity and weight control: conflicting findings. Current Opinion in Clinical Nutrition and Metabolic Care. September 2011. [Link]
Kenny, Paul J. Reward Mechanisms in Obesity: New Insights and Future Directions. Neuron. February 2012. [Link]
Luke, Amy and Cooper, Richard S. Physical activity does not influence obesity risk: time to clarify the public health message. International Journal of Epidemiology. December 2013. [Link]
Mayo Clinic Staff. Weight loss: Feel full on fewer calories. Mayo Clinic. March 4, 2014. [Link]
Johns, David A., et al. Diet or Exercise Interventions vs Combined Behavioral Weight Management Programs: A Systematic Review and Meta-Analysis of Direct Comparisons. Journal of the American Dietetic Association. October 2014. [Link]
Mekary, Rania A., et al. Physical activity in relation to long-term maintenance after intentional weight loss in premenopausal women. Obesity. January 2010. [Link]
Mekary, Rania A., et al. Weight training, aerobic physical activities, and long-term waist circumference change in men. Obesity. February 2015. [Link]
Shomaker, Lauren B., et al. Eating in the absence of hunger in adolescents: intake after a large-array meal compared with that after a standardized meal. The American Journal of Clinical Nutrition. October 2010. [Link]
