A Calorie's a Calorie, or is it?

Certainly that's what we preach. A calorie's a calorie - if you were to eat the exact same number of calories daily it wouldn't matter where those calories came from they'd have the same effect on your weight.

Or would they?

I'm very comfortable saying I'm wrong, and while I'm not quite willing to do that in the a calorie is a calorie case yet, I'm a bit closer today due to an article I read yesterday in the journal Obesity.

The article looked at 42 green monkeys who were followed for 6 years. They were fed one of two diets that were designed to "maintain" their study starting weight by providing them each with 70 Calories per kg of green monkey weight. What varied in these diets was the percentage of fat that came from trans fats with one group of monkeys getting 8% of their fat from trans fat sources while the other group had less than 1% of fat from trans fat sources.

Otherwise, the sample diets were pretty much the same.

The results were surprising. The trans fat group's weight increased by roughly 7% while the other group gained less than 2% with the trans fat group having gained more fat intra-abdominally (the less healthy place to gain it). The researchers also found that post meal insulin levels in the trans fat group were 3x higher than in the non-trans fat group and there was a reduction seen in tissue biopsy of the trans fat group's insulin receptors' abilities to trigger a response.

The authors conclude that trans fats are in fact independently associated with both weight gain and the preferential distribution of weight intra-abdominally resulting in an impairment of glucose tolerance which in turn is of course a risk factor for the development of type II diabetes.

This was definitely a neat study and while I'm not yet ready to stop telling people a calorie's a calorie, I'm eager to see some studies that try to tease out whether this is applicable to humans or just to green monkeys.

To be sure however, this study is yet one more piece of damning evidence against the inclusion of trans-fat in our diets.