Meg Farris / Eyewitness News

BATONROUGE, La. -- Over the years, people on Weight Loss Wednesday have sworn by diets that alter one of the three macronutrients: proteins, carbohydrates or fats.

There are 'low fat' and 'low carb' diets, and people who say 'high protein' changed their lives.

But now award-winning science found the answer to which is best.

Remember the Ideal Protein diet craze? People were taking in such low carbs with high protein that some would pass out if they tried to exercise. But they lost lots of weight.

Well now there is top-rated science that cuts through all the hype and advertising and marketing buzz. A doctor and researcher says he has proof of what makes you fat and what makes you lose weight when it comes to carbs, proteins and fats.

'(It) is one of the most important, if not the most important factor,' said Endocrinologist Dr. George Bray, who is the chief of the Division of Clinical Obesity and Metabolism at Pennington Biomedical.

Dr. Bray has done extensive research at LSU's Pennington Biomedical Research Center in Baton Rouge. It's recognized worldwide for its research in obesity, diabetes, heart disease, cancer and dementia.

People such as Daniel Kuhn sign up and get paid to live at the center as research subjects.

'You got a lot of inner peace. You had to confine a lot in very confined space, but I found my self very relaxed. I was reading a lot of books. I started my memoirs. I was writing. I was doing a lot of constructive things,' said Kuhn, 30, of Zachary, La., who works in the service end of the hotel industry. He was 25 when he joined the study.

But before we talk about the latest ground breaking findings, let's look back to Dr. Bray's study published in 2009. He took four diets -- one low fat, one high fat, one normal protein, one high protein. Each patient's metabolism was measured to see how many calories were needed for everyday living. Then everyone's calories were cut by 750, never going below 1,200 a day.

So which group lost the most weight?

'The weight loss over the first year was, six months and year, was exactly the same in all four groups. And when we followed them out to two years where we had 80 percent of our people participating, again there was no difference in weight loss with any of the four diets,' said Dr. Bray.

So it's calories -- measurement of food energy -- that count.

Now let's fast forward to his current study recently honored as the lead article of the year in the Journal of the American Medical Association (JAMA).

That's where Kuhn comes in. He was one of the young, healthy men and women test subjects who lived at Pennington for three months. There was no exercise allowed. Body composition, calories and metabolism were carefully and precisely measured.

It was measured with a DXA (DEXA) scan, special machines where a hood is placed over the patient's head and in a room called a metabolic chamber. The participants in the study had to spend 24 hours locked in the room. It actually measured how much oxygen they were breathing in, how much carbon dioxide was coming out, and their urine output, so the doctors could get their exact metabolism, meaning they could tell exactly how many calories they were burning.

'I did bring my Xbox along and that did allow me to keep some form of sanity during that time period,' said Kuhn about his time in the small chamber with only a bed and half bathroom.

This time Dr. Bray studied protein. The patients either got low protein, normal protein or high protein diets. And they were made to gain weight.

'So we overfed them about them about 1,000 calories a day for eight weeks,' explained Dr. Bray.

So did the high protein group gain less body fat than the others?

'What we found was that the protein didn't make any difference in whether you, how much fat you stored. You stored exactly the same amount on each of the three protein diets,' Dr. Bray said.

But while they all gained the same amount of fat, those on the normal protein and high protein diets weighed more.

'We don't know whether they gained muscle or just water,' he said.

Dr. Bray is figuring that out now by analyzing the data from the study. But he suspects they did not gain good, lean, solid muscle, since you need to workout and lift weights to use the extra protein to build muscle.

But while overeating any type of calorie causes weight gain, there are some things you need to know. Not enough protein in your diet will cause you to lose muscle and slow your metabolism. While protein is more filling, in science that doesn't translate to people eating fewer calories.

And those calories in soft drinks and fruit juices aren't very well sensed by the body, so that can make you not lower your food calories to compensate.

'Fructose has some very bad effects on its own. And the quantities we now get from the sugar in our diet, high fructose corn syrup in our diet, are clearly not healthy for many people,' Dr. Bray emphasized.

So the take home message:

'The calories you eat are the calories you're going to keep,' Dr. Bray said.

Dr. Bray said the best diet is to eat the nutritious foods that you like while controlling the portions. Because if you like the food, you are more likely to stay with it long term.

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