by Matthew W. Gillman, MD, SM
Most of us have neglected this thermic effect because we’ve believed there’s not much we can do about it. But that may not be true.
For clues, let’s look at bariatric surgery. In rats, and probably in humans too, the gastric bypass procedure ratchets up the thermic effect of food to twice normal levels. There’s not enough research yet on the newer sleeve gastrectomy procedure.
One of the most interesting things I learned a couple of weeks ago at a conference sponsored by the NIH Obesity Research Task Force is that this effect of bariatric surgery may act through major changes in the intestinal microbiota. Every one of us has about 3 times more bacterial cells in our bodies than we do native human cells, and just about all of the bacteria live in our gut. Obese mice, rats, and humans have different types of gut “flora” than do their lean counterparts. After bypass surgery in rodents, a new gut flora emerges, different from the ones in obese or naturally lean animals. Some experiments now raise the possibility that these bacteria are responsible for increased thermogenesis of ingested food and could be one of the reasons that many patients maintain weight loss well after their surgery.
Even though eating whole grains and foods with protein induce more heat production than others, claims of “fat burning foods” on the covers of magazines at the checkout counter are exaggerated. But I will be on the lookout for interventions that cause long-term change in our microbiota to enhance the thermic effect of what we eat. Perhaps we’ll figure out ways, short of bariatric surgery, to include them in conjunction with improved diet and more physical activity for longer-lasting weight loss.