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.
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I wouldn't think calories are equal. Since our bodies consume foods in different matters, I would think they use calories in different manners.
ReplyDeleteWhenever I hear or read about a gravity defying study that shows not all the universe’s calories are created equal, I usually stop, pause, take a breath . . . and read the details of the study. In this case the study: Trans Fat Diet Induces Abdominal Obesity and Changes in Insulin Sensitivity in Monkeys, published in Obesity (vol.15, No. 7, July 2007) basically follows a cohort of African green monkeys from a young age followed up for 6 years. One group was assigned a diet of primarily cis-fatty acid and the other a mix of cis and trans-fatty acids. How the assignments came about is not defined; however, the cis fatty acid fed group from the start weighed less. According to Figure 1 of the original paper, the cis-fat fed monkeys weighed roughly 6.4 kg on average and the trans-fat fed animals 6.6 kg. The ages of the animals, as reported in the methods, ranged from 4 to 13 years with an overall average age of 8 years. What was the age breakdown of the individual groups? Information not reported is always suspect in my world.
ReplyDeleteNot only did the authors gloss over the assignment of animals to either the cis or trans diet and report no significant difference in weight from the start of the study, but cited no specific statistical test to justify it—just a p value. Regardless, if the trans-fat fed cohort is larger on average from a very early age and followed over 6 years of maturation, small differences in initial weight might be magnified by natural body growth (small differences in human stature at an early age predicts large differences later in life). The study would have been much more believable had they spent an inordinate effort to randomize the subjects from a uniform age and blind the reviewers. Instead we have a study wasting NIH funds and leading the cheer against trans-fats.
Excellent points, especially your point on small variations in weight leading to longer term variation with natural aging.
ReplyDeleteI felt the study was interesting enough for me to want a better study done, but you're absolutely right, we're not given enough methodologic data to get too excited - this notwithstanding the fact that we're talking about monkeys.