Mindset Can Boost Metabolism? Not So Fast...

Would that it were so. That just thinking that what you eat is an indulgent treat could diminish your hunger later and ramp up your calorie-burning.

The possibility arose from a 2011 study that was just recently described in an NPR report headlined "Mind Over Milkshake: How Your Thoughts Fool Your Stomach." It describes what happened when clinical psychologist Alia Crum mixed up a giant batch of vanilla milkshake, then labeled cups of it differently for two groups of subjects: Some were told it was a virtuous low-calorie drink while others were told it was a decadent indulgence.

Crum reported that when people thought they'd just indulged, their bodies — specifically their levels of ghrelin, a hunger-related hormone — responded as if they'd taken in more calories than people who believed they'd had a low-cal shake. Possible moral of story: Your beliefs about the food you eat — based on, say, reading labels — could affect how your body responds.

It's a provocative thought and a fun yarn — and a super-fun video, at the bottom of this post — but perhaps a bit too fun. The reality checkers at Nutrition Action -- which is put out by the nonprofit Center For Science in the Public Interest — have just responded to the story with a big "Really?" And a headline: "Can Your Mindset Boost Metabolism? It's not as straight-forward as one recent study suggests."

An excerpt:

First of all, the study never measured ghrelin’s effect on metabolism (or even how much food the participants ate at their next meal). Nor have others.

“If you give animals ghrelin injections either subcutaneously or directly into the brain, they increase their food intake, increase their body weight, and burn less fat,” says Jenny Tong, an associate professor of endocrinology and a ghrelin expert at the University of Cincinnati who was not involved in the milkshake study. But giving ghrelin to cancer patients who are losing weight doesn’t help much, she says.

“In normal humans, we only have very short-term studies measuring changes before or after meals. To say that ghrelin has such a profound effect on metabolism, the evidence in humans is lacking.”

Among the uncertainties:

Ghrelin boost. Ghrelin dropped more when people drank the ‘indulgent’ shake in part because ghrelin had climbed more during the 40 minutes they spent looking at the labels before drinking. Odds are, that’s because the high-calorie label depicted an ice cream sundae.

And a bit more:

In a similar study, ghrelin levels were no lower after people ate a yogurt that was labeled “high-calorie” than after they ate an identical yogurt that was labeled “low-calorie.”

“The findings of the milkshake study are intriguing,” says Tong. “But it’s not as simple as just saying that ghrelin increases or decreases after a meal and that explains how our body regulates metabolism. That’s a bit of a stretch.”

Seems like nothing is ever simple when it comes to diet. Perhaps that's a point on which both sides could agree.

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Carey Goldberg Editor, CommonHealth
Carey Goldberg is the editor of WBUR's CommonHealth section.



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