A new study appeared in the American Journal of Clinical Nutrition today showing that people who ate the most protein, especially animal protein, had the least abdominal obesity.
Danish researchers studied 22,570 woman and 20,126 men aged 50-64 years for five years to determine changes in waist circumference as a function of macronutrient intake. At the start of the study subjects filled out food frequency questionnaires (FFQ) to determine their intake of specific foods. Readers of this blog know I’m critical of FFQ, but in this case the researchers validated the FFQ with 7 day dietary diaries, which, I believe, adds more strength to the study than if FFQ were solely relied upon. Researchers measured the waist circumference of the subjects then rechecked them 5 years later. After correcting for smoking and activity level, the intake of fat, protein, carbohydrate and alcohol was correlated to increase in abdominal circumference.
The findings were interesting.
This study showed that total energy or energy from each of the 3 macronutrient groups–carbohydrates, fat, and alcohol–were not associated with subsequent DWC [difference in waist circumference] in either women or men, whereas an inverse association with protein intake was observed.
An inverse association with protein intake. An inverse association means that the two variables move in opposite direction. In this case, it means that as protein intake went up, waist circumference went down. In other words, those subjects who reported eating the highest amount of protein had the least increase in waist size over the following five years.
The researchers divided the macronutrients into different groups to see if there were any specific sub-groups that appeared to cause or prevent waist size increase. The idea for doing this came from the notion that perhaps there were offsetting effects. Since there was no overall correlation with carbohydrate intake, for example, maybe those subjects who got their carbs from vegetables had a decrease in waist circumference while those who got the same amount of carb from sugar had a comparable increase offsetting the decrease from the former.
As the researchers drilled down into the data that is exactly what they found.
When the macronutrients were divided into subgroups on the basis of the contributing food sources, significantly different associations were seen for some of these groups. There was an inverse association with animal protein and a direct association with vegetable fat.
So, the correlation with animal protein was even stronger than with just protein in general. And there was a direct association with vegetable fat intake, which means that the subjects consuming the most vegetable fat had the largest increases in abdominal size over the next 5 years.
In women, a partition model showed that DWC was inversely related to intake of carbohydrate energy from fruit and vegetables, whereas intake of carbohydrate energy from food sources with simple sugars or from added sugar was positively associated with DWC. A clear and significant positive association with intake of carbohydrates from refined grain and potatoes was observed…
So, there you have it. At least in women, carbs from vegetables and fruits equate to smaller waist; those carbs from potatoes, sugar and refined grains make the belly expand.
An interesting aspect of this study, to me, at least, was the fact that there was NO correlation with an increase or decrease of waist size with caloric intake. It wasn’t the number of calories consumed that caused the change, it was what those calories were made of. So, that makes this another one of the growing list of studies that throws a wrench into the works of the a-calorie-is-a-calorie set. As we all know, it’s not just the caloric content of the food we eat, it is also what those calories do to us metabolically.
To anyone who understands that calories have an effect beyond the amount of energy they provide, this study makes perfect sense. For those who can’t see beyond the energy content, this study is a real head scratcher.
At some point someone in academia is going to realize that the old calories in equals calories out model doesn’t work. I read a paper recently from a researcher at the University of California at San Francisco who is sniffing around the edges, but based on the conclusions he has drawn, the depth of his dumbth is of cavernous proportions. I’m saving his paper for a future post.
The take home message from this Danish study is that if you want to minimize the growth of your abdomen over time, you should eat meat, avoid vegetable oil, eat non-starchy fruits and vegetables and avoid sugar and refined grains. Hmmm, I’ve heard that somewhere else.