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Which is more important for weight loss: Dieting or exercising?

Let's get one thing straight: there's no magic bullet to losing weight. It requires hard work and effort. But the latest weight-loss research presented in a popular New York Times article suggests that we might be spending too much time burning calories at the gym while ignoring the real culprit: diet.

"For long-term success you do need both," CBS News medical contributor Dr. Tara Narula, a cardiologist at Lenox Hill Hospital in New York, told "CBS This Morning." "In terms of where your money is, where the biggest return on investment is, it's with diet and caloric restriction."

Narula said that because of misconceptions about weight loss, people often overeat and assume that they can burn off the excess calories at the gym. But "it's easier to take out the calories than to try and burn them off," she said. For example, for an individual with a daily caloric intake of 3,500 to drop a pound of fat, it would take one and a half times as long to lose weight through exercise burning 200 calories per day than through cutting 500 calories a day from their diet.

"That's either an hour or an hour and a half at the gym on the treadmill, on the rowing machine; or it's cutting out a couple sodas, a bagel with cream cheese, a cupcake," Narula said.

Of course, exercise is also important to maintain weight loss long-term and to build muscle mass. "It also has other benefits to lower your blood pressure, your cholesterol, help you process blood sugar, help you sleep better, help your mood," Narula said.

Losing weight also gets harder as we age. Metabolism decreases by about 2 percent per decade, Narula said. The struggle also becomes more difficult because of our biology. "So after three to six months of losing weight your hormones start to change and it makes it tougher for you to lose wight," Narula said. "So increased hormones actually increase appetite and increase food storage."

Those hormonal shifts last for about a year after you've lost weight, Narula said.

She emphasized that losing weight is "extremely difficult, but extremely important."