But, as I reported on HealthBeat in 2008, physicians who treat obese and overweight patients know that only about 5% of us are able to lose weight and keep it off—even in highly controlled experimental settings where patients diet and exercise under a doctors' supervision. Over two years, 95% of us will put the pounds back on, and in some cases, add more.
A National Institutes of Health (NIH), working group study published in the January 2015 issue of the journal Obesity, confirms that: "Despite advancements in our understanding of obesity, weight regain after weight loss remains the most substantial problem in obesity treatment – with both the body and the mind conspiring against individual efforts to maintain weight loss."
What Randomized Controlled Trials Reveal
University of Minnesota Psychologist Traci Mann has spent 20 years running an eating lab and, based on her experience, she reports: "Long-term weight loss happens only to the smallest minority of people."
Indeed, when she and five other researchers analyzed outcomes for patients in randomized trails where one group dieted, and the other group did not, the studies showed that, after two years, the average patient on a calorie restricted regimen had lost only one kilogram, or about two pounds, while one third to two thirds of dieters had actually regained more weight than they lost. (In many of these trials, the patients not only cut calories, but also exercised.)
What about folks who combine intensive lifestyle changes with drugs designed to help us lose weight? "Studies show that patients on drug therapy lose around 10 percent of their excess weight," but "the weight loss plateaus after six to eight months," UCSF's Medical Center reports. "As patients stop taking the medication, weight gain usually occurs."
Low-Carb vs. Low-Fat Diets
Does it matter which diets you try?
At one time, most physicians were convinced that fatty foods led to obesity, and a low-fat diet offered the best route to becoming svelte. But in recent years, a growing number of doctors and health advocates have begun to argue that increased consumption of sugar and refined carbohydrates is the most likely explanation for our obesity epidemic.
Last summer WIRED published an impressive in-depth review of what we do and do not know about whether certain foods will make us fat.
The story notes that that in 2009, "Robert Lustig, a pediatric endocrinologist, rose to national fame after a 2009 lecture in which he called sugar 'poison' went viral on YouTube.
Meanwhile, newer science has undermined the consensus that fat is all that bad for you. A recent meta-analysis published in the Annals of Internal Medicine found no clear evidence that eating saturated fat contributes to cardiovascular disease."
What about carbs? "In trials, carbohydrate restricted diets almost invariably show significantly better short term weight loss," WIRED reported, but "over time, the differences converge towards non-significance." In other words, the available evidence suggests that over the long term, both low-fat and low-carb diets fail.
Why Is Losing Weight, and Keeping it Off, So Difficult?
We don't know.
The cruel truth is that obesity is an incredibly complicated disease. Physicians and scientists who specialize in studying it acknowledge that medical science still has not yet sliced through the tangle of genetic, metabolic, social, psychological and environmental factors that cause most of us to regain whatever weight we lose.
The conventional wisdom tells us that shedding fat is simple: just eat fewer calories than you burn. In other words, put less food in your mouth, and exercise more. As the post above reveals (URL) many family doctors and GP's still believe this. After all it was only two years ago that the American Medical Association acknowledged that obesity is a "disease."
(If they didn’t think obesity was a disease, what did they think it was? I’m afraid that, like many in our culture, deep down, they viewed obesity as a sign of sin. Actually, two sins: “gluttony” and “sloth.” My guess it that this is true of doctors who were, themselves, overweight– and felt guilty about it.)
2008—What We Knew Then
Seven years ago, when I first wrote about a PBS documentary titled "Fat: What the Experts Don't Tell You" I learned that, for most people, the received wisdom doesn't work. Eating less and moving more does not lead to long-term weight loss. (Let me add: I highly recommend this film. It is by turns, moving, entertaining, and eye-opening. It will tell you what most of the mainstream media may never reveal about losing weight.)
In the documentary, Harvard's Dr. Lee Kaplan, head of the Weight Reduction Program at Mass General Hospital, acknowledges that: "Obesity doesn't seem like a subtle disease. But it is. If something is off kilter by just 1 percent in your system that can lead to a 100- pound weight gain. More than 400 genes are involved in weight regulation. And that doesn't include the environmental factors."
In that 2008 post, I also quoted Arthur Frank, medical director of the George Washington University Weight Management Program: "People think that dieting is 'a matter of choice.'" In other words, with a little will power, you can simply choose to eat less. But in fact, losing weight requires overcoming powerful brain signals that are working against you.
Dr. Michael Rosenblaum, a Columbia University researcher who, at the time was working on an NIH-funded study on weight control, explains: "Obesity is the one disease where your body fights the cure. By and large, the body is programmed to help you heal." But not in this case.
If you ever have dieted you already know that, once you lose some weight, your metabolism seems to slow down, and stops burning as many calories. For all your body knows, you are stranded on a desert island, starving to death. So it tries to "save you." Some argue that this is how the human species has survived.
"We are very efficient biological machines," says University of Alberta health professor Tim Caulfield, who writes about health misconceptions. "We evolved not to lose weight. We evolved to keep on as much weight as we possibly can.”
But saying that your body fights weight loss does not shed light on the more fundamental question of how and why your metabolism slows—or why you hit a plateau—and ultimately re-gain the weight you lost.
Not everyone believes that this is all about evolution. Some argue that the obesity epidemic has more to do with what we eat today— and how compulsively we diet–See part 2 of this post, below