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Excess Calories, Not Protein, Contributes to Weight Gain

Weight gain is a major concern for many of us, especially after all the excess during the holidays. But is it just certain foods that cause us to get fat, or is it simply overindulging – regardless of the type of foods – that contribute to weight gain?

A recent study published in the Journal of the American Medical Association (JAMA) suggests that when it comes to weight gain, the only factor that matters is how many calories are consumed.

In the study, conducted by Dr. George A Bray and his colleagues at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, 25 subjects between the ages of 18 to 35 with a body mass index (BMI) ranging from 19 to 30 were analyzed under a controlled setting to analyze the impact of protein intake in weight gain, energy expenditure and body composition.

After going through a weight-stabilization period of 13 – 25 days, the subjects were split into three groups. The first group of randomly selected participants was fed a low-protein diet with only 5% of their energy coming from protein. The second group was fed a “normal” diet, with 15% of their energy intake coming from protein. The third group was fed a high-protein diet consisting of 25% protein.

Each of the diets, which were followed for 8 weeks, contained 40% more energy than the diets provided during the stabilization period, the equivalent of 954 additional calories per day.

By the end of the study, all participants gained weight, regardless of gender or protein intake. Participants in the low-protein group gained an average of 7 lbs, those in the normal-protein group gained an average of 13.3 lbs and members of the high-protein group gained an average of 14.4 lbs. The lower weight gain in the low-protein group was attributed to a failure to increase lean body mass.

Importantly, in the low protein group, more than 90% of the excess calories were stored as fat. In the normal and high protein groups, this number was closer to 50% with most of the rest of the excess energy consumed (thermogenesis).

For those in the low-protein group, lean body mass (total body mass minus fat mass) decreased during the overeating period, at an average of 1.5 lbs. However, for the participants in the normal and high-protein groups, lean body mass increased by an average of 6.3 lbs and 7 lbs, respectively.

Resting energy expenditure (how much energy your body burns while at rest) differed by group. In the normal and high protein groups, an increase of 160 calories per day and 227 calories per day, respectively were found. In contrast, resting energy expenditure did not increase in the low-protein group.

Ultimately, the study found that calories alone account for the increase in body fat. Additionally, protein affects energy expenditure and storage of lean body mass, but not body fat storage.

The Bottom Line

We often equate weight with fat, but it is vital that we learn to distinguish between the two. Weight is a measurement of our total body mass – both lean body mass and fat mass.

It is easy to forget that “muscle” or lean body mass is heavier by volume than fat – and contributes to more calories burned, even when we’re doing nothing. So as long as our weight is not fat weight, it is not necessarily a bad thing. We want to have lean body mass, and protein is a necessary component in building lean body mass.

What this study tells us is that too much of anything, even protein, will contribute to excess calories. Excess calories, regardless of the type, will turn into fat. Conversely, not getting enough protein can cause loss of lean body mass and this reduces our body’s ability to burn calories efficiently.

Keeping a watchful eye on caloric intake is critical to weight management. This can be a challenge, especially if you eat out on a regular basis. But, eating at restaurants doesn’t mean you have to sabotage your diet.

January’s Journal of Nutrition Education and Behavior includes a study that shows women can lose weight, even when eating out at restaurants, as long as they are educated about eating. Learning about portion sizes, hunger cues, and what we eat are the best ways to maintain a healthy weight.

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