Where Does Fat Go When You Lose Weight? Mostly Into Thin Air

(Phoney Nickle/Flickr)

(Phoney Nickle/Flickr)

By Richard Knox

A couple of years ago, Ruben Meerman took off 40 pounds. And that got him wondering: What exactly happened to all that fat?

Conventional wisdom was that he “burned” it off. Or sweated it off. Or excreted it. None of that satisfied Meerman, who has a physics degree and makes his living explaining science to schoolkids and for the Australian Broadcasting Corporation.

So Meerman tackled the problem and eventually came up with a surprising answer: Most of the lost fat disappears into thin air.

More specifically, 84 percent of those fat molecules get exhaled as colorless, odorless carbon dioxide. The other 16 percent departs the body as H-2-O — plain old water.

Meerman says the discovery “got me really excited because I’d stumbled onto a gap in the knowledge. It struck me as remarkable that no one had thought this was interesting enough to pursue.”

The British Medical Journal thought so too. It has published a paper, co-authored by biochemist Andrew Brown of the University of South Wales, in its annual Christmas issue, which features off-beat (but peer-reviewed) research.

Weight Loss Realism

Meerman hopes the work will dispel misconceptions held by health professionals as well as the general public. And, he hopes it will provide a helpful dose of realism to counter the impossible expectations millions have about weight loss.

If people understand where the fat goes (and how), they’ll get “why there’s a limit to how quickly you can lose weight,” Meerman said in a Skype interview from Sydney. “And if you understand the limit, you won’t be so quickly depressed if you don’t lose 20 pounds in the first two weeks.”

First, the misconceptions. Meerman and Brown surveyed 150 professionals — split equally among family doctors, dietitians and personal trainers — about where they think the fat goes during weight loss.

By far the most common answer was that the fat was transformed into energy or heat — that is, “burned off.” About two-thirds of doctors thought so. A slightly higher proportion of dietitians did too, and about 55 percent of personal trainers.

But that would violate the Law of Conservation of Mass. It’s a basic precept of chemistry, formulated in 1789 by the French scientist Antoine Lavoisier, which holds that mass is neither created nor destroyed in chemical reactions. The total mass at the end must equal the mass at the starting point — even if matter is quite transformed in the process, from solid to liquid or gas.

The Energy Of A Bomb

Meerman points out that if fat were transformed into pure energy during weight loss, the results would be cataclysmic. Continue reading

Eat Fat But Stay Thin: Mice Can Do It, Maybe Someday We Can Too

Generic lab mice

Generic lab mice

The journal Nature reports that some lab mice have lived out my food fantasy: Even though they ate a heavy, high-fat diet — my particular dream is unlimited Ben & Jerry’s — they did not become obese, because researchers found a novel way to tweak their metabolism.

Sigh. The caveats first: What works in mice might not in humans. It might not be safe. Clinical trials are not on the immediate horizon. This is no reason to stop eating healthy food and exercising.

But we can dream, right? And we can savor the explanations from Dr. Barbara Kahn of Beth Israel Deaconess Medical Center and Harvard Medical School, senior author on the Nature paper. She sums up: “We found an enzyme in fat that appears to be elevated in people with obesity and diabetes. And if we inhibit it in mice, we can increase the amount of energy that the animal burns, and thereby decrease the amount of calories that are stored as fat.”

It’s something like the extra energy you burn when you exercise, she said — except without the exercise.

Dr. Kahn’s team found a gene that, when suppressed, makes metabolism less efficient — which is actually a good thing if you’re trying to avoid obesity.

“Generally, in our lives, we think it’s good to be efficient — and it certainly is good to be efficient in time management,” she said. “But if your metabolism is efficient, it means you need fewer calories to generate the energy that cells need for their basic metabolism, and therefore, if you eat too many calories, you will put on weight. But if the cells are inefficient, they’ll burn up those extra calories and you won’t put on weight.”

So do these findings — centering on an enzyme known as nicotinamide N-methyltransferase or NNMT — indeed hold the promise of some sort of drug to prevent or treat obesity?

“The approach we used in the mice was mainly prevention,” Dr. Kahn said, “but the same idea should work for treatment of obesity. I have to caution, of course: one has to look into all the safety aspects if one considers such a treatment in humans. But all the cellular machinery is there, so it should work.” Continue reading

The ‘Fat But Fit’ Myth Debunked

On the train to New York for Thanksgiving, we sat next to a family with a very chubby girl. She was about 9, with lovely red hair and a pretty moon-shaped face. But I could see her belly bulging and her chunky arms as she played with her iPad, and I imagined some tough teenage years ahead.

While her mother slept, her dad headed to the cafe car and returned with a box of chocolate chip cookies and peanut M&M’s. “Quiet,” he said, handing the treats to the girl. “Eat them before Mom wakes up.” Then he gave her a Mountain Dew to wash it all down. It was 10 am on Thanksgiving.

“Child abuse,” I thought, but kept my mouth shut.

I imagined the little red-haired girl again today, in light of this headline in MedPage Today “Fat But Fit — Is It Just A Myth?”

Remember the concept of “benign obesity” — the idea that as long as you’re exercising and relatively fit, being a little fat probably won’t hurt you. Well, think again. A new study published in the Annals of Internal Medicine suggests there is no healthy obesity. According to the news report:

Metabolically healthy obese people have a long-term increased risk for death and cardiovascular events compared with their normal-weight counterparts, suggesting there is no such thing as benign obesity, according to a meta-analysis.

(Yale Rudd Center for Food Policy & Obesity)

(Yale Rudd Center for Food Policy & Obesity)

When studies with follow-ups of a decade or more were considered, obese people with no metabolic abnormalities had a 24% increased risk for these events compared with metabolically healthy, normal-weight people (relative risk 1.24; 95% CI 1.02-1.55), reported Caroline K. Kramer, MD, PhD, of Mount Sinai Hospital in Toronto, and colleagues.

All metabolically unhealthy people had a similar elevated risk for the events compared with metabolically healthy, normal-weight study participants, they wrote in the Annals of Internal Medicine, specifically an RR of 3.14 for normal weight (95% CI 2.36-3.93), 2.70 for overweight (95% CI 2.08-3.30), and 2.65 for obese (95% CI 2.18-3.12).

“Our results do not support this concept of ‘benign obesity’ and demonstrate that there is no ‘healthy’ pattern of obesity,” Kramer and colleagues wrote. “Even within the same category of metabolic status (healthy or unhealthy) we show that certain cardiovascular risk factors (blood pressure, waist circumference, low high-density lipoprotein cholesterol level, insulin resistance) progressively increase from normal weight to overweight to obese.”

Timing of Large Meal Matters For Weight Loss, Study Finds

Dieters take note: Eating earlier in the day may help you shed pounds.

Indeed researchers from Brigham and Women’s Hospital and the University of Murcia in Spain found that it’s not only what you eat but when you eat that matters when it comes to losing weight.

(Photo courtesy Brigham & Women's Hospital)

(Photo courtesy Brigham & Women’s Hospital)

The observational study, published in the International Journal of Obesity, found that among a group of overweight or obese Spanish diners, those who ate a late lunch (after 3 p.m) showed slower weight-loss rates and lost significantly less weight than folks who ate lunch earlier (before 3 pm). Notably, there was no significant difference in overall calories consumed by either group or their estimated energy expenditures, said senior author Frank Scheer, PhD, MSc, director of the Medical Chronobiology Program and assistant professor of medicine at Harvard Medical School. Rather, “the timing of meals predicted weight loss effectiveness,” he said.

(As is often the case in Mediterranean countries, lunch is the main meal of the day; for these study participants, it made up about 40 percent of total caloric intake for a 24-hour period.)

Scheer said the study corroborates earlier animal studies in which meal timing determined weight gain in mice.

So, what’s going on here?

Scheer said one hypothesis is that when you eat meals at “abnormal” times there may be a disruption of the normal synchrony of metabolic clocks in various organs. Continue reading