A few weeks ago Tara Parker Pope wrote The Fat Trap for the NYT and once I read it I started sending it to other doctors I know. It is a great summary on the current knowledge of why we get fat, and more importantly for those of us that already are tipping the scales, why is it so damn hard to take that weight back off. (I’ll discuss Young, Obese and Getting Weight Loss Surgery nearer the end)
Beginning in 2009, he and his team recruited 50 obese men and women. The men weighed an average of 233 pounds; the women weighed about 200 pounds. Although some people dropped out of the study, most of the patients stuck with the extreme low-calorie diet, which consisted of special shakes called Optifast and two cups of low-starch vegetables, totaling just 500 to 550 calories a day for eight weeks. Ten weeks in, the dieters lost an average of 30 pounds.
At that point, the 34 patients who remained stopped dieting and began working to maintain the new lower weight. Nutritionists counseled them in person and by phone, promoting regular exercise and urging them to eat more vegetables and less fat. But despite the effort, they slowly began to put on weight. After a year, the patients already had regained an average of 11 of the pounds they struggled so hard to lose. They also reported feeling far more hungry and preoccupied with food than before they lost the weight.
Who among us can’t identify with that story? If you can’t you’ve been thin all your life and can go suck an egg. But for those that have carried extra pounds it’s part of the yo-yo routine of dieting. But why is this? Were we permanently programmed for a preset weight and will feel as though were starving below it? If this is the case, why is obesity increasing now, in the last 20 years? The answer suggested is more subtle, but the fascinating thing is, your body’s set weight might be a real thing. It’s just not programmed from birth.
The key finding seems to be that when we become obese, our body sets whatever maximal weight we obtain as “ideal”, and subsequent loss of weight, even to a normal healthy weight, results in a extended or possibly permanent state of hunger.
While researchers have known for decades that the body undergoes various metabolic and hormonal changes while it’s losing weight, the Australian team detected something new. A full year after significant weight loss, these men and women remained in what could be described as a biologically altered state. Their still-plump bodies were acting as if they were starving and were working overtime to regain the pounds they lost. For instance, a gastric hormone called ghrelin, often dubbed the “hunger hormone,” was about 20 percent higher than at the start of the study. Another hormone associated with suppressing hunger, peptide YY, was also abnormally low. Levels of leptin, a hormone that suppresses hunger and increases metabolism, also remained lower than expected. A cocktail of other hormones associated with hunger and metabolism all remained significantly changed compared to pre-dieting levels. It was almost as if weight loss had put their bodies into a unique metabolic state, a sort of post-dieting syndrome that set them apart from people who hadn’t tried to lose weight in the first place.
For years, the advice to the overweight and obese has been that we simply need to eat less and exercise more. While there is truth to this guidance, it fails to take into account that the human body continues to fight against weight loss long after dieting has stopped. This translates into a sobering reality: once we become fat, most of us, despite our best efforts, will probably stay fat.
I think of it more like when you’ve become obese you’ve set the cruise control to that weight. It might be too high, but whenever you dip below that weight from then on, your body will try to compensate to bring you back up to speed (or to fat). While it’s true that consistently, weight loss regimens have failed to show a durable weight loss in study populations, we know durable weight loss is possible. It is possible to lose weight and keep it off, it’s just difficult, and people rarely manage weight loss in the long term. But rather than ending there Pope goes into what has made those who do manage the weight loss successful.
The National Weight Control Registry tracks 10,000 people who have lost weight and have kept it off. “We set it up in response to comments that nobody ever succeeds at weight loss,” says Rena Wing, a professor of psychiatry and human behavior at Brown University’s Alpert Medical School, who helped create the registry with James O. Hill, director of the Center for Human Nutrition at the University of Colorado at Denver. “We had two goals: to prove there were people who did, and to try to learn from them about what they do to achieve this long-term weight loss.” Anyone who has lost 30 pounds and kept it off for at least a year is eligible to join the study, though the average member has lost 70 pounds and remained at that weight for six years.
There is no consistent pattern to how people in the registry lost weight — some did it on Weight Watchers, others with Jenny Craig, some by cutting carbs on the Atkins diet and a very small number lost weight through surgery. But their eating and exercise habits appear to reflect what researchers find in the lab: to lose weight and keep it off, a person must eat fewer calories and exercise far more than a person who maintains the same weight naturally.
So basically, once your body, used to being obese, drops weight, it permanently tries to get you to eat more, and employs metabolic strategies to conserve energy. This was confirmed by other experiments rigorously monitoring the body’s metabolic activity:
Leibel and his colleague Michael Rosenbaum have pioneered much of what we know about the body’s response to weight loss. For 25 years, they have meticulously tracked about 130 individuals for six months or longer at a stretch. The subjects reside at their research clinic where every aspect of their bodies is measured. Body fat is determined by bone-scan machines. A special hood monitors oxygen consumption and carbon-dioxide output to precisely measure metabolism. Calories burned during digestion are tracked. Exercise tests measure maximum heart rate, while blood tests measure hormones and brain chemicals. Muscle biopsies are taken to analyze their metabolic efficiency. (Early in the research, even stool samples were collected and tested to make sure no calories went unaccounted for.) For their trouble, participants are paid $5,000 to $8,000.
Eventually, the Columbia subjects are placed on liquid diets of 800 calories a day until they lose 10 percent of their body weight. Once they reach the goal, they are subjected to another round of intensive testing as they try to maintain the new weight. The data generated by these experiments suggest that once a person loses about 10 percent of body weight, he or she is metabolically different than a similar-size person who is naturally the same weight.
The research shows that the changes that occur after weight loss translate to a huge caloric disadvantage of about 250 to 400 calories. For instance, one woman who entered the Columbia studies at 230 pounds was eating about 3,000 calories to maintain that weight. Once she dropped to 190 pounds, losing 17 percent of her body weight, metabolic studies determined that she needed about 2,300 daily calories to maintain the new lower weight. That may sound like plenty, but the typical 30-year-old 190-pound woman can consume about 2,600 calories to maintain her weight — 300 more calories than the woman who dieted to get there.
Scientists are still learning why a weight-reduced body behaves so differently from a similar-size body that has not dieted. Muscle biopsies taken before, during and after weight loss show that once a person drops weight, their muscle fibers undergo a transformation, making them more like highly efficient “slow twitch” muscle fibers. A result is that after losing weight, your muscles burn 20 to 25 percent fewer calories during everyday activity and moderate aerobic exercise than those of a person who is naturally at the same weight. That means a dieter who thinks she is burning 200 calories during a brisk half-hour walk is probably using closer to 150 to 160 calories.
Another way that the body seems to fight weight loss is by altering the way the brain responds to food. Rosenbaum and his colleague Joy Hirsch, a neuroscientist also at Columbia, used functional magnetic resonance imaging to track the brain patterns of people before and after weight loss while they looked at objects like grapes, Gummi Bears, chocolate, broccoli, cellphones and yo-yos. After weight loss, when the dieter looked at food, the scans showed a bigger response in the parts of the brain associated with reward and a lower response in the areas associated with control. This suggests that the body, in order to get back to its pre-diet weight, induces cravings by making the person feel more excited about food and giving him or her less willpower to resist a high-calorie treat.
“After you’ve lost weight, your brain has a greater emotional response to food,” Rosenbaum says. “You want it more, but the areas of the brain involved in restraint are less active.” Combine that with a body that is now burning fewer calories than expected, he says, “and you’ve created the perfect storm for weight regain.”
The body is a machine. It requires energy input, and when there is a deficit, or an excess it will expend more stored fuel or add stored fuel. This has not changed, but amazingly the body has tricks to make it’s fuel usage more efficient in response to a perceived shortage of fuel – or rather, a perceived loss of fuel reserves. The net effect of what it can do isn’t incredibly dramatic. About a 10% increase in efficiency can be overcome by further lowering caloric intake, but it speaks to what a pain it is to lose weight as your body’s biology automatically modifies to sabotage your diet while sending your brain signals that food will make you happier.
This article is also really depressing because it suggests once you’ve gone overweight, you basically will have to stay on a diet for life to keep weight off. And the people that succeed need to be permanently calorie-obsessive.
Kelly Brownell, director of the Rudd Center for Food Policy and Obesity at Yale University, says that while the 10,000 people tracked in the registry are a useful resource, they also represent a tiny percentage of the tens of millions of people who have tried unsuccessfully to lose weight. “All it means is that there are rare individuals who do manage to keep it off,” Brownell says. “You find these people are incredibly vigilant about maintaining their weight. Years later they are paying attention to every calorie, spending an hour a day on exercise. They never don’t think about their weight.”
What does this mean for you? For starters, the most important obesity intervention is prevention. Clearly, once you are obese, your body will work against weight loss (although the amount of time with the excess weight is unknown, transient weight gain is likely not going to bump up your cruise control). From a young age we need to encourage regular excercise, Don’t cook Paula Deen’s diabetes inducing food, and I think the new federal health care bills emphasis on screening for childhood obesity might result in earlier, and likely more efficacious intervention. Obesity panacea points out this should not be hard, you just have to limit your sleeping and sitting to 23.5 hours a day. Second, if you are now overweight (I gained about 30 pounds in my first two years of residency) if you wish to lose the weight you will have to commit to a permanent alteration of your food intake to less than it would be for someone of a similar weight who had never been fat. In other words, you’ll always have to eat fewer calories than you probably would like. In six months back in the lab I’ve lost the 30 pounds, but my experience is consistent with this report, I’m eating less now than what I was before to maintain this weight. This is extremely irritating. It reminds me of David Letterman after he disappeared for a while, came back tanned and lean, and someone asked him what’s his secret to weight loss, and he replied, “I’m always hungry.”
I’d say the flaw of the article is that it doesn’t mention weight loss surgery which can be an intervention that works long term a majority of the time. The problem is it is higher risk, and carries a mortality rate of about 1:2000-1:1000, and a complication rate of about 1-3%. This means that the therapy is reserved for those who have a very high BMI, the superobese, or that have a high BMI in addition to medical problems for which weight loss would strongly control their risk factors for death. In Young, Obese, and in Surgery, the issue is, what about the minimum age for using weight loss surgery as an intervention? In it a 17-year-old girl is profiled, weighing about 271 lbs before surgery (she finally got it at age 19), at a height of 5’1″. However, while the BMI is appropriate for surgical intervention, I’m worried that psychologically, it will be a failure, and this might be generalizable to teenagers in general. For instance, here’s an excerpt of some pre-surgical conversations:
In December 2010, Ms. Gofman, who had just turned 19, and her mother arrived at the office of Dr. Danny Sherwinter, the wiry, fast-talking chief of bariatric surgery at Maimonides Medical Center in Brooklyn, for a consultation. Ms. Gofman was nervous but eager.
She had been sold on the Lap-Band, the only operation Dr. Sherwinter performs, because it is reversible and relatively low risk. She weighed in at 271 pounds, with a body mass index of 51, well above the minimum B.M.I. of 40, or 35 for people with at least one other related health problem, that was required for the use of the Lap-Band. (In February, the F.D.A. reduced the minimum B.M.I. for patients with another problem to 30, the threshold of obesity.)
Ms. Gofman’s mother asked what would happen if her daughter wanted to get pregnant. The band would be decompressed, Dr. Sherwinter said, and “basically you’re a normal pregnant woman, eating your pickles and ice cream.”
“Yummy,” Ms. Gofman said.
“What about the skin?” her mother, Judith, asked, meaning loose skin that might develop after weight loss.
“That’s going to be an incredible conversation,” Dr. Sherwinter said. “Let’s just get there first.”
He told Ms. Gofman that, going by the averages, she could expect to lose about 40 percent of her excess weight, or 70 to 80 pounds. “Which is better than any diet out there,” he said. “We’d be looking for you to come in around 200.”
But, he warned, “If you don’t follow along the average way, like have a milk shake every night or don’t exercise at all, you will end up in the worser half.”
Dr. Sherwinter asked her to prepare for surgery by going on a liquid diet. But she privately reasoned, “I’m about to have surgery, so I might as well enjoy myself.”
One of the major issues with weight loss surgery is appropriate selection of patients that will benefit. The bariatric surgeons I’m familiar with usually insist on a year long process, starting with 6 months of attempted weight loss, supervised by a physician and nutritionist. If that fails (as it did for this woman), you then have to go to educational seminars on the implications of the procedure, the risks, the permanent diet modifications, etc., you have to undergo a psychiatric evaluation, and then sign a contract with the surgeon indicating you’ll comply with a full set of changes to lifestyle including exercise (beginning immediately after surgery – they make them walk around the ward multiple times post-op to prevent the most worrisome complication of pulmonary embolism). This is because even with a limited gastric pouch created by lap-band or sleeve-gastrectomy, or with that combined with decreased absorption from a Roux-en-Y gastric bypass, you can still sabotage your weight loss. Usually this is done using very high-calorie liquids, like soda and smoothies. And frankly if you start out obese and your major source of excess calories is 4 liters of coke a day, the surgery will likely fail you.
Now, immediately pre-op, the patient was asked to do one simple thing, start on a liquid diet in preparation, and what does the teenager say? “I’m about to have surgery, so I might as well enjoy myself.” Surprise, surprise. The teenager knows better than her surgeon.
This might be borne out by other studies in the literature:
Another study in Australia found that one-third of operations on teenagers required follow-up surgeries within two years, often because of “pouch dilation,” when the stomach above the band becomes enlarged, which can happen if the patient does not follow the regimen and tries to eat too much.
I tend to agree with the arguments against doing this operation on teenagers:
But that, said Diana Zuckerman, a psychologist and president of the National Research Center for Women and Families, goes to the heart of why teenagers are bad candidates for bariatric surgery: they are often immature, rebellious and uninterested in long-term consequences.
“It’s not just you can’t eat Thanksgiving dinner,” Dr. Zuckerman said. “You’re going to have to have this tiny little meal for the rest of your life.”
A more critical question is whether surgery can lead to malnutrition, particularly in bypass patients because their shortened digestive tracts absorb fewer nutrients, which could affect bone growth, sexual maturation and other development.
“Kids across the country are getting this surgery, and we need to know the consequences,” said Dr. Mary Horlick, project scientist for the National Institutes of Health, which is sponsoring a study of bariatric surgery in about 250 teenagers.
Surgeons who operate on teenagers say the alternative is worse: a lifetime of obesity, ostracism and diseases like diabetes. Dr. Jeffrey L. Zitsman, director of the center for adolescent bariatric surgery at NewYork-Presbyterian/Morgan Stanley Children’s Hospital, says that among the biggest obstacles are pediatricians and family doctors, nearly half of whom, according to a recent medical journal article, say they would never refer a teenager for obesity surgery.
Sure enough, for the teen in this story, the surgery had unfortunately little impact:
She would wolf down her food, and then she would run to the bathroom to vomit or sit in pain waiting for it to make its way through the band. “I couldn’t even have a single little sandwich without embarrassing myself and going to the bathroom,” she said.
To her dismay, she discovered that “all the fattening foods” — chips, chocolate — went down easily. “Apples and bread are hard,” she said. “It’s annoying how hungry I was.”
Ms. Gofman started to feel judged by some of her friends. “Some will ask a dumb question, like, how’s the surgery going?” she said. She felt like telling them, “You obviously can tell it’s stalled, right?”
By fall, she had canceled her gym membership because it was too expensive. When the hospital urged her to come in for a visit, she said she was busy. But the truth was that she had aged out of the child health insurance program, and she was embarrassed to be gaining weight.
She finally confessed to the hospital that she could not pay. The physician assistant told her they would “work it out.”
Ms. Gofman, who has just turned 20, saw Dr. Sherwinter in November. She had regained not quite half of what she had lost. He did not scold or blame her. He tightened her band, so it now took an hour and a half to force down two scrambled eggs.
To me this is a tough story. She experienced an initial loss that was significant, but lost most of that ground when she discontinued exercise and likely failed to stick to the diet. There is no hard conclusion, but I wouldn’t really call this a success story, at least not as successful as bariatric surgery can be in the adult population. I feel the article undersold surgery for adults, and suggested we don’t know what the long term outcomes are. This is not so, cohort studies have suggested significant reductions in mortality (90% decrease in relative risk of mortality) compared to weight-matched controls in surgical patients, surgery decreases the mortality from cardiovascular events by half, and surgical efficacy for weight loss and correction of comorbidities of obesity is excellent. For example see this 2004 systematic review in JAMA:
A random effects model was used in the meta-analysis. The mean (95% confidence interval) percentage of excess weight loss was 61.2% (58.1%-64.4%) for all patients; 47.5% (40.7%-54.2%) for patients who underwent gastric banding; 61.6% (56.7%-66.5%), gastric bypass; 68.2% (61.5%-74.8%), gastroplasty; and 70.1% (66.3%-73.9%), biliopancreatic diversion or duodenal switch. Operative mortality (≤30 days) in the extracted studies was 0.1% for the purely restrictive procedures, 0.5% for gastric bypass, and 1.1% for biliopancreatic diversion or duodenal switch. Diabetes was completely resolved in 76.8% of patients and resolved or improved in 86.0%. Hyperlipidemia improved in 70% or more of patients. Hypertension was resolved in 61.7% of patients and resolved or improved in 78.5%. Obstructive sleep apnea was resolved in 85.7% of patients and was resolved or improved in 83.6% of patients.
These procedures work. Complications of the procedures, including frequent re-operation for the lab band group, are real issues. But the data shows a durable weight loss and decreased mortality. The procedures do work. Personally, I’m not a big fan of the lap band because I think you have a decrease in issues up front, but longer term they seem to cause more problems. But their relatively easy reversibility is very appealing.
Using these procedures on teenagers though, I’m less enthused about. For one, they have a substantial amount of time to reverse obesity through conventional means before serious damage is done to their body. Two, they are simply not mature enough to grasp the implications of such a life-altering procedure (and for such a great portion of their life) and they are going to fail more frequently because they have known issues with poor judgement, impulse control, and risk assessment. This will result in unhappy patients a decade later, and who needs that? I can’t think of a minimum age that would be appropriate, but I think certainly for adults between 18-25 a smart surgeon would screen this population with much more stringency than an older population. And I agree with the pediatricians, this probably should not be done at all on minors, for similar reasons.