Pound for Pound, Worst Foods for Weight Gain

Portion Control and Small Steps Keys to Success

Lovera said he definitely cut down his portion sizes, and he learned the value of gradually replacing some of the bad foods with healthier options.

He said he never ate a lot of potato chips. His weakness was tortilla chips. He loved indulging in a plate of nachos.

"Now, I buy oranges and apples," he said. "I have an apple or an orange in the middle of the afternoon."

He also said he never drank a lot of soda or sugary drinks, but enjoyed them when he ate out. Whatever he drank then he now replaces with sparkling water.

"The little changes really helped a lot," he said.

The bottom line is not to eat less, but to eat less unhealthy, said Dr. Beverly Green, a scientific investigator at the Group Health Research Institute.

"Buy real food, preferably foods that are environmentally sustainable," said Green. "Avoid restaurants, bags and boxes, unless you know the product is very healthy."

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Many nutrition experts hope there will be many more people like Lovera who realize that little things really do mean a lot when it comes to weight loss.

"If people can slowly change their behaviors -- eating one spoonful less, adding veggies a few times a week -- they can improve health and change their body weight," said Diekman.

The research also assessed other lifestyle factors, like sleeping habits. The study found sleeping less than six hours a day or more than eight hours a day was also associated with weight gain.

Physical activity, on the other hand, was linked to weight loss. Experts have long stressed the importance of being active as part of a healthy lifestyle.

Lovera started walking for about 10 minutes a day and worked his way up to a 25-minute walk during lunch and another walk in the evenings. And, he said, he's proof that cutting out a lot of the foods associated with weight gain can lead to successful weight loss.

He only has seven more pounds to lose to reach his target weight of 170 pounds, a healthy weight for someone who is 5 feet 10 inches tall. He believes that with the changes he's made in his life, he can stay in that range. He also hopes his story can inspire others to take those same small steps.

"I feel like a person who's more in control of my life and my future," he said. "I feel as if I've gotten my life back."

Additional reporting by ABC News' Bojana Zupan and Jane Kurtzman.