Diet or exercise? To lose weight, do both

A: Oh, yes, it's that time of year again: time to kick those New Year's resolutions into high gear, dust off the weight and food scales, hit the gym, and ask critical questions about losing weight. (However, I wish more people asked, "What does it take to keep lost pounds off?" Just sayin'!)

For starters, let's define what is meant by exercise.

There are two main types of exercise. Aerobic exercise is defined as rhythmic, full-body physical activity that causes your heart rate to increase. The latest government physical activity guidelines recommend that adults get at least 2 1/2 hours of moderate-intensity aerobic exercise a week or an hour and a quarter of vigorous-intensity activity, or a combination of both.

Resistance training is the other main type of exercise. It's defined as exercise that strengthens major muscle groups by challenging them to near-exhaustion in eight to 12 repetitions. The same guidelines recommend that adults engage in muscle-strengthening activities at least twice per week.

Research exploring the health hazards of our sedentary culture has generated recommendations to add reducing sedentary behavior as a third exercise goal. Sedentary behavior is defined as all behaviors associated with sitting and reclining for which you expend low levels of energy and burn minimal calories. According to the American College of Sports Medicine, long periods of sedentary activity have, independent of the amount of aerobic and resistance training one does, emerged as a risk factor for the development of prediabetes, Type 2 diabetes, and heart and blood-vessel diseases. Goal 1: Don't go more than 90 minutes without moving (other than when you're sleeping).

Regular exercise has been called the best medicine for health and longevity because of its long list of physical and mental health benefits. Yet the sad fact is that just under half of all American adults meet the physical activity recommendations for aerobic activity and only one-fifth meet the guidelines for both aerobic and resistance exercise.

And now to the debate in question.

A recent British Journal of Sports Medicine editorial offers an apt bottom line: "You cannot outrun a bad diet. . . . [Exercise] isn't enough when it comes to losing weight or staying healthy."

In fact, it's hard to outrun, or outwalk, even a healthy eating plan if you eat more calories than your body burns. Think about it: Walking a mile burns roughly 100 calories, equivalent to a large piece of fruit or a couple of tablespoons of mixed nuts. Hardly indulgent!

"Research shows the most effective way for most people to lose weight is to pair a calorie-conscious healthy-eating plan with adequate exercise," Jim White, a registered dietitian nutritionist and exercise physiologist and owner of Jim White Fitness & Nutrition Studios, told me in an email. He added that high-intensity aerobic exercise along with reduced calories is more likely to take off weight compared with doing only resistance training. Cranking up the exercise without trimming calories doesn't typically result in weight loss.

"Changes in diet are usually required to lose weight," Kevin Hall, who does metabolism research at the National Institute of Diabetes and Digestive and Kidney Diseases, told me in an email. Hall added that most people lose less weight than they expect by doing exercise for two reasons. First, they might become less active at other times of the day. Second, they might eat more, possibly because they think they burned more calories with exercise than they did.

Translating this research, I tell clients that paying careful attention to their daily calorie intake wins the Academy Award for best actor and exercise takes home the Oscar for best supporting role.

As for the role of exercise in helping you keep pounds off for good, it's a must. Regular exercise can help compensate for the metabolic slowdown that commonly results from significant weight loss. Hall explains it this way: When people who have been overweight lose weight, they typically burn fewer calories than someone at that same weight who has never been overweight.

Keeping weight off requires making up the difference either by decreasing calorie intake or increasing physical activity. People tracked in the National Weight Control Registry, which regularly surveys those who've lost weight and kept it off for years, report doing about an hour of exercise a day. They also minimize their sedentary behavior, such as watching television.

Simply put, exercise isn't the sole answer to losing weight or keeping pounds off, but it's an important part of the equation.

Another essential element is to zero in on a healthy eating plan that helps you control the calories you eat most of the time, leaving some wiggle room for less-healthy food choices on occasion. Make sure your eating plan fits your needs and doesn't call for you to radically change how you're accustomed to eating. And last but not least, you've got to be persistent in practicing those healthy lifestyle behaviors.