(CNN) -- Sujit Bhattacharya knew he felt sluggish and had trouble putting on his socks and shoes. One day, when he tried on a pair of size 30 shorts, his wife pointed out that they fit only under his belly.
Sujit Bhattacharya says losing weight has improved his frame of mind. He is shown in 2006, left, and 2007.
Yet Bhattacharya, of Coppell, Texas, never paid attention to his weight problem until his doctor told him he had high cholesterol in summer 2006. His friends also told him that he had become heavy and needed to do something about it.
The feedback was upsetting, he acknowledged, but the combination of his friends' prodding and the cholesterol numbers motivated him to start trimming down his 193-pound frame.
"I needed some tough love: things I didn't want to hear but needed to hear," Bhattacharya said.
He researched how to lose weight extensively on the Internet, including CNN.com's health section. He learned that 3,500 calories add up to one pound of weight and tried to figure out how to eat to decrease his daily caloric intake.
Instead of eating a few large meals every day, he ate six small meals, keeping track of how many calories he consumed. He had been eating more than 2,500 calories a day, perhaps 3,000, so he cut this down to 1,500 calories a day. That meant losing a pound every two or three days.
"As long as you know how many calories you need and how many calories you eat, it's just math," he said.
He also included more fruits and vegetables in his diet and ate fewer fatty meats. For exercise, he changed his routine from three days a week of limited cardio and heavy weights to six days a week with the same heavy weights but increased cardio.
In six months, he lost 40 pounds. Since then, he's put on about 5 pounds of "good" or muscle weight but has otherwise sustained his new physique through diet and exercise.
Today, at age 39, he said he's starting to look more like when he was in high school.
Losing weight has improved Bhattacharya's overall frame of mind, he said. He also noticed that he doesn't get colds or the flu and fights off infections faster than before. iReport.com: Share your success stories
Sometimes Bhattacharya wonders why he didn't start losing weight earlier and can say only that he felt "fat, dumb and happy."
"I didn't understand what I was doing was hurting me," he said.
He actively encourages friends to try his weight loss method. One friend lost 20 pounds following his advice. See more photos of weight loss success stories from iReport.com »
"What I tell friends is: You've got to have a burning platform, something to make you start, a goal or desire," he said. "For me, it was the bad cholesterol test and friends. Someone else may want to fit into a bikini in the summer."
Dietitians say they would encourage others to follow Bhattacharya's example of reducing calories and spreading them more throughout the day instead of eating big meals.
If you try it, make sure you have enough energy, feel good while doing it and eat foods you enjoy so you can stick to it long-term, said Dawn Jackson Blatner, a registered dietitian and spokeswoman for the American Dietetic Association.
In fact, Bhattacharya did twice as well as the average person in a weight loss program, Blatner said. He lost 20 percent of his body weight in six months, beating the national average of 10 percent.
Tara Gidus, ADA spokeswoman and team dietitian for the NBA's Orlando Magic, recommends that women never eat fewer than 1,200 calories and men no fewer than 1,500 calories per day.
She typically does not recommend cutting out 1,000 calories at a time, "but if someone is really motivated to lose weight and they eat snacks that are filling in between meals, then they can cut a significant number of calories, lose weight and not feel overly hungry," she said.
Blatner said she would also encourage anyone who wants a drastic diet change to consult a doctor.
Bhattacharya emphasizes that anyone can shed unwanted pounds as long as he or she compares the number of calories needed to maintain weight and the number of calories he or she eats.
"I firmly believe it is not hard to lose weight," he said.
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