The more weight one carries, the harder it is to exercise. But to fight the obesity epidemic — now the nation’s No. 2 preventable cause of death, just behind tobacco use — there’s simply no way around it: You have to move your body.

Nutrition and fitness experts like Kara Mitchell know that can be hard if you’re already overweight, a description that now applies to two-thirds of us. But it’s nowhere near impossible. The key? Baby steps.

“Lots of times, we go into an all-or-nothing mind-set,” said Mitchell, senior exercise physiologist and dietitian at the Duke Center for Living in Durham, N.C., where reliance on oxygen tanks or walkers won’t stand in the way of a good workout. “Even going for a five-minute walk after work is better than doing zero.”

Angie Oakley knows what it’s like to fail at exercise. Growing up in Garner, N.C., she played flag football and softball. In her early 20s, she was diagnosed with Crohn’s disease, which can cause abdominal cramps, joint pain and other digestive problems. She needed surgery twice. After days of a liquid diet, Oakley would scarf down anything she could get her hands on. Two children and two marriages later, her weight had crept up from 165 to 235.

At 34, she found herself breathless at the top of the stairs. She couldn’t play soccer with her two young daughters.

This year, Oakley decided she needed more than a gym where employees would show her how to use a piece of equipment, then walk away.

She turned to the Rex Weigh program at Rex Wellness Center in Raleigh, N.C., a combination of nutritional guidance and personal trainer-directed exercise.

Mitchell thinks of physical activity as a pyramid. At the base are activities of daily living, such as walking to your car. To make sure you’re moving enough, put the trash can 10 feet away from your desk so you have to get up to use it, she said. Take the stairs instead of the elevator. Don’t just sit in a chair when you’re talking on the cordless phone at home. Try a pedometer. If you start out at 2,000 steps a day, try to increase the number gradually.

Oakley has lost 29 pounds since January. She wants to lose about 40 more. But she’s noticed other changes, too. Climbing the stairs is easier now. She has more energy. Her friends tell her she looks good.

In the past, Oakley didn’t think she had an hour three times a week to exercise. Guilt about leaving her girls nagged at her. But she knows that they enjoy the gym’s child-care area and that she’s becoming healthier for them. She doesn’t intend to quit this time.

“I keep telling (her personal trainer), ‘I’m not dead yet,'” Oakley said. “‘So just bring it on.'”