Suppose you were reading the health section of a newspaper looking for ideas on how to lose weight, and you came across an article that started like this:
Whether you are just starting a New Year’s diet or struggling to maintain a healthy weight, a provocative new study offers some timely guidance. It isn’t so much what you eat, the study suggests, but how much you eat that counts when it comes to accumulating body fat.
The findings are the latest in a string of studies to challenge claims that the secret to healthy weight loss lies in adjusting the amount of nutritional components of a diet—protein, fat and carbohydrates.
I don’t know about you, but I’d assume that provocative new study involved adjusting the nutritional components of a diet – protein, fat and carbohydrates. Let’s check:
In the study, to be published in Wednesday’s issue of the Journal of the American Medical Association, 25 young, healthy men and women were deliberately fed nearly 1,000 excess calories a day for 56 days, but with diets that varied in the amounts of protein and fat.
Hmmm … it appears that the provocative new study which supposedly proves the secret to healthy weight loss isn’t a matter of adjusting the ratio of protein, fat or carbohydrates is
1) a study of people who intentionally gained weight instead of losing weight
2) manipulated the balance of fat and protein, but not carbohydrates.
Let’s read on:
While those on a low-protein diet—about 5% of total calories—gained less weight than those on a normal- or high-protein regimen, body fat among participants in all three groups increased by about the same amount. Typical protein consumption is about 15% of calories, while the U.S. government recommends it make up between 17% and 21% of total daily calories.
The findings suggest that it matters little whether a diet is high or low in fat, carbohydrates or protein, it’s calories that build body fat.
It matters little whether or a diet is high or low in fat, carbohydrates or protein? I must be missing something here … did the researchers change the ratio of carbohydrates in the diet nor not?
The patients in the Pennington study ranged in age from 18 to 35 and had BMIs between 19 and 30. (Between 25 and 30 is considered overweight.) They lived at the center’s metabolic unit for between 10 and 12 weeks and were fed the 1,000 extra calories a day for the final eight weeks of their stay. Carbohydrates were held steady at about 41% to 42% of calories while fat levels varied with the protein regimen.
Brilliant. Study subjects were put on three different diets designed to induce weight gain, the carbohydrate ratio was virtually the same across all three groups, and yet media health reporters are telling us the provocative study proves that manipulating the fat, carbohydrate or protein content of a diet won’t help us lose weight.
After eight weeks, all participants in the study gained weight. The 16 men and nine women made similar gains. The low protein-diet group gained about seven pounds, about half the 13.3 pounds added on by the normal protein participants and 14.4 pounds put on by the high protein group.
If you read the full study (which I did), you’ll learn that the low-protein group didn’t gain as much weight because – despite overeating by 1,000 calories per day – they lost muscle mass. The other two groups gained muscle mass, with the high-protein group gaining the most. I’d say that’s an important difference. Losing muscle mass is a great way to slow your metabolism. Gaining muscle mass raises your metabolism. The results listed in the study seem to confirm that point:
The low protein diet had 6% of energy from protein, 52% from fat, and 42% from carbohydrates. The normal protein diet had 15% of energy from protein, 44% from fat, and 41% from carbohydrates. The high protein diet had 26% of energy from protein, 33% from fat, and 41% from carbohydrates.
Overeating produced significantly less weight gain in the low protein diet compared with the normal protein diet group or the high protein diet. Body fat increased similarly in all 3 protein diet groups and represented 50% to more than 90% of the excess stored calories. Resting energy expenditure, total energy expenditure, and body protein did not increase during overfeeding with the low protein diet. In contrast, resting energy expenditure and body protein (lean body mass) increased significantly with the normal and high protein diets.
Elsewhere in the study, the researchers provide more details: the low-protein group lost an average of 1.5 pounds of lean body mass, while the high-protein group gained an average of 7 pounds of lean body mass. When you overeat by 1,000 calories per day and still lose muscle, you know it’s a lousy diet.
The effects on metabolism may not have produced significant differences in fat accumulation in the short duration (less than two months) of this study, but I suspect that since the low-protein group was losing muscle mass, we’d see more of a difference over time. Interestingly, the researchers didn’t say exactly how much extra body fat each group gained. They only told us the difference wasn’t significant:
The overall increase in fat mass for all 3 groups was 3.51 kg (95% CI, 3.06 to 3.96 kg) from baseline and was not significantly different between the 3 groups (P = .89), although the low protein group added on average more than 200 g of fat (about 2000 kcal).
I also found these paragraphs interesting:
With the low protein diet, more than 90% of the extra energy was stored as fat. Because there was no change in lean body mass, the 6.6% increase in total energy expenditure reflects the energy cost of storing fat and is close to the estimate of 4% to 8% for fat storage derived by Flatt. With the normal and high protein diets, only about 50% of the excess energy was stored as fat with most of the rest consumed (thermogenesis).
The extra calories in our study were fed as fat, as in several other studies, and were stored as fat with a lower percentage of the excess calories appearing as fat in the high (25%) protein diet group.
I’m confused … if the low-protein group stored 90% of their extra energy as fat, while the other groups only stored 50% of their extra energy as fat, how did they all end up gaining the same amount of body fat?
Maybe I’m just not getting the math involved, but never mind. Even if all three groups did gain the same amount of body fat, this study doesn’t really tell us anything about how to effectively lose weight, and it certainly doesn’t prove anything one way or another about the effects of manipulating the carbohydrate content, since the carbohydrate ratios were virtually identical.
Another researcher who commented on the study in a Reuters article put it nicely:
Donald Layman, a food science researcher at the University of Illinois in Urbana, said it’s difficult to see how the findings apply to a general population that isn’t being overfed such a protein-deficient diet, in the case of the low-protein group.
“It’s an interesting scientific study, but from an obesity standpoint, I don’t think it tells us anything,” he told Reuters Health.
Bingo. Even if the protein ratio made little or no difference on fat accumulation in an over-eating study conducted in a metabolic ward, most of us aren’t trying to get fatter. We’re trying to get leaner. And we don’t live in metabolic wards where our meals are prepared for us and every calorie is tabulated. We live in the real world where we don’t (and can’t) count every calorie, and where the amount of food we eat is determined by our appetites. Protein is satiating. When we eat higher-protein foods, we tend to eat less. When we eat high-carb meals, many of us find our appetites going all out of whack, and we eat more.
The lead researcher for the study was George Bray, who seems to have dedicated his career to proving that the federal government’s dietary guidelines are correct – and if he has to cleverly design studies to achieve that goal, or write conclusions that aren’t backed up by the actual data, by gosh he’ll do it.
It was Bray who conducted the study on salt restriction that I mentioned in my Science For Smart People Speech, the one in which a drastic reduction in dietary sodium produced a whopping two-point drop in blood pressure. Based on that meaningless result, Bray concluded that sodium restriction is an effective means of controlling hypertension. (Say what? Two points is a meaningful reduction in blood pressure? I don’t think so.)
Here’s Bray offering his conclusion from the latest study:
“If you over-eat extra calories, no matter what the composition of the diet is, you’ll put down more fat.”
Really, Dr. Bray? If you wanted solid scientific evidence that the composition of the diet is meaningless, why was the ratio of carbohydrates the same in all three groups? Since you blasted Gary Taubes in your review of Good Calories, Bad Calories, we know you’re well aware of the hypothesis that it’s carbohydrates, not protein or fat, that promote fat accumulation … so why didn’t this provocative study include a group that restricted carbohydrates? After all, none of the low-carb diet gurus recommend anything close to a ratio of 40% carbohydrates.
I think the answer to that question can be found near the end of the study.
This study was supported in part by the US Department of Agriculture.