But an article in last week's Time magazine created a buzz in the blogosphere by questioning the value of the exercise part of the weight-loss formula.
Doctors who treat overweight and obese patients were not pleased -- even if there was evidence to support the claim.
"Yes, we have a magic drug for cholesterol, we have magic drugs for high blood pressure, but we don't have a magic pill for weight," said Dr. Martha Gulati, associate director of the Women's Heart Center at Northwestern Memorial Hospital in Chicago.
"To bring out a public health message that we should not exercise? That's absolutely the wrong message," Gulati said.
The article, "Why Exercise Won't Make You Thin" by John Cloud, argued that in the real world, exercising vigorously may just increase a person's appetite and use up their natural reserves of self-control. After a hard workout, it's just human nature to eat back those calories with an extra treat, or burn fewer by taking the elevator instead of the stairs, Cloud argued.
He pointed to a study published in February in the online journal PLoS One to back up his claims. The study followed 411 women who were divided into four exercise groups -- no exercise required, 72 minutes per week, 136 minutes per week and 194 minutes per week of monitored exercise.
Doctors found that at the end of the six-month study, the women who exercised the most didn't lose as much weight as the researchers predicted. The group with the moderate amount of exercise lost an average of 4.6 pounds while the group with the most vigorous of exercise lost just 3.3 pounds, though they had been predicted to lose an average of about 5 pounds.
"No matter how much exercise you do or don't do, your diet matters -- it's extremely easy to eat back more calories than you burn," said Dr. David Katz, "Good Morning America" medical contributor and director of the Yale University of Prevention Research Center.
But Katz said the "ah ha, exercise is not good for weight loss" idea troubles him and many other doctors who counsel people trying to lose weight.
Is Weight All Americans Care About?
"What do people care about? Do they simply care about their dress size or do they care about their health?" Katz said. "If you care about your health, exercise is your best friend."
Katz pointed out that three behaviors -- not smoking, exercising and eating right -- have "a massive influence on your medical destiny."
If people care only about losing weight, Katz quipped, "Why don't you just infect yourself with cholera? It would work for weight loss."
Katz and many others who treat obesity agree exercise must not be ignored because of its importance for overall health, even if it doesn't make as big of an impact on the scale as people believe.
Exercise for Weight Loss or Weight Maintenance?
"The diet has the biggest bang for the buck initially, but when it comes to weight maintenance, but there's no doubt that exercise keeps it off," said Gerald Endress, a clinical exercise physiologist and fitness director at the Duke Diet and Fitness Center in Durham, N.C.
"I exercise so that I can eat more. I think a lot of us do exercise so we can maintain our weight," he said.
Yet while Endress could see why excessive exercising may lead some people into a tailspin of overeating to compensate for hunger, he has seen the opposite in his fitness center every day. The people exercising there, Endress said, always lose weight.
"If you look, shows like 'The Biggest Loser,' they're overexercising them [the participants] tremendously and they're losing weight," Endress said.
Even if the people in Endress' fitness center didn't lose weight by exercising, diet and nutrition experts point out that the gym-goers would likely be losing fat and gaining muscle.
The Scale Is Not the Only Measure of Health
"It's one of those things where everybody would like to believe that, people will say 'I don't lose weight but I'm exercising,'" said Keith-Thomas Ayoob, director of the nutrition clinic at the Albert Einstein College of Medicine in New York.
"I say, 'Are you losing inches?'" Ayoob said.
Ayoob and Katz pointed out that many people gain weight when they embark on an exercise program because they are gaining muscle.
Katz recounted the story of a man who weighed 400 pounds when he first came to him for a fitness regimen.
"He'd work hard and the loss of body fat was huge, but he'd step on the scale and see no change," Katz said. "But if I am converting body fat into muscle, that's spinning straw into gold."
Ayoob added that while exercise alone might not trim pounds as fast as diet alone might, the mere change in lifestyle when someone adopts a workout routine may lead to fewer calories ingested.
"What exercise also does in terms of weight loss -- it can make you more sensitive to when you're hungry and when you're not," Ayoob said. "And it does something else: It gets you out of the house; it gets you off the sofa so you're not having the temptation of going back and forth between the refrigerator."