(Chicago Tribune) -- "Maybe you love to eat but hate to exercise," Jim Karas proposes.

For most of us, that about sums it up.

Karas wants to help you get over the exercise part of that equation.

"The biggest hurdle you will ever face in losing weight isn't sticking to a diet or going to the gym every day. It's simply this: getting started," he says.

Can you spare 15 minutes, three times a week? Trainer and author Karas says that's enough to get you off to a good start.

"If you're doing nothing, this is absolutely a step in the right direction," says Karas, who blogs (and sells his fitness products) at jimkaras.com. Just those 45 minutes weekly will rev up your metabolism, increase your energy, and make you look and feel better, he says.

Karas brags that after an appearance years ago on "Good Morning America," he cornered Diane Sawyer and delivered the bad news: She needed to lose 25 pounds. "She was shocked, but I got her attention." (And became her trainer to help her do it.)

For those of us who aren't Diane Sawyer, who have put off starting an exercise program, he insists that we don't need to spend hours a week on a treadmill.

"You don't have to have equipment. You don't have to go to the gym," he says.

Instead, Karas recommends taking three basic exercises -- pushups, Pilates planks, and squats or lunges -- and doing each until "you're almost out of breath." Then repeat the series "until you fill up 15 minutes" three times weekly. Instructions for all of these are all over the Internet.

And yes, he disagrees with federal guidelines that recommend 75 minutes a week of vigorous aerobic activity (or 2 1/2 hours of moderate exercise).

In most exercise regimens, "the neglected variable is intensity," Karas says. "If you really get in there and get the job done, you optimize results and you save yourself time."

(c)2012 the Chicago Tribune Distributed by McClatchy-Tribune News Service.