At last count, nearly two of three (64.5 percent) Americans were classified as overweight or obese. With this number climbing upward at an alarming rate, there has been much speculation as to the cause of America’s weight problem. Some diet books are especially vocal about naming carbohydrates as the culprit. A few years back, the villain was dietary fat.

Somewhere along the line, concern about calories took a back seat. That’s too bad, because you gain weight when you eat more calories than you burn. Period.

“Obesity is a disease of excess — excess calories and excess sedentary activities,” says registered dietitian Keith Ayoob, Associate Professor of Pediatrics at the Albert Einstein College of Medicine in New York. “The cure is to balance calories in with calories out.”

Likewise, weight loss doesn’t depend on whether calories come from carbohydrates, protein, or fat. To lose a pound, you must create a 3,500-calorie deficit by consuming fewer calories, burning more calories through physical activity, or a combination of both.

            This formula is simple in theory but difficult for many people to put into practice. Food intakes, activity behaviors, and environmental factors all play a role in tipping the balance toward weight gain. For instance for a number of foods, portion sizes have increased along with the amounts Americans eat. Our enthusiasm for a labor-saving lifestyle contributes to the fact that only about one in four adults gets even the minimum recommended amount of daily physical activity.

            Fortunately, the calorie equation can be balanced with increased attention to both food and physical activity habits. Experts offer this advice:

RECORD FOOD INTAKE TO RAISE EATING AWARENESS

We are often surrounded by tempting foods and often do not realize how much we are eating. Keep a written log of what you eat. You may be amazed when you see how many calories you are getting from seemingly innocent habits like nibbling food samples at the grocery store.

CHANGE FOOD HABITS

Cutting calories does not mean a life sentence of food scales and measuring cups, as some people fear. Dr. Ayoob recommends that overweight patients gradually start trimming food portions by, for instance, filling their plates a little less or skipping second helpings. “The weight starts to come off when people change their eating habits, not by counting every calorie,” he says.

FIND THE RIGHT MACRONUTRIENT MIX

            Although a calorie deficit is necessary for weight loss, choosing the right proportions of carbohydrates, protein, and fat in the diet can have a positive impact. Many women take the “low fat” message to extremes. They are hungry all the time because they don’t eat enough protein and fat for satiety. By evening, they can be ravenous and eating is out of control. The 2002 National Academy of Sciences recommends that adults obtain 45 to 65 percent of their total daily calories from carbohydrates, 20 to 35 percent from fat, and 10 to 35 percent from protein.

CRANK UP CALORIE-BURNING PHYSICAL ACTIVITY

            In addition to keeping a food log, keep a physical activity log. People usually overestimate their amount of physical activity, but few actually get enough. When you have been inactive, start with just a few minutes of daily physical activity, such as walking, and build up from there. For more seasoned exercisers, increase your frequency or intensity by 50 percent. People benefit in terms of calorie burning when they go from 2 days to 3 days of exercise each week, or increase your workout time from 30 minutes to 45 minutes.