The Diet Age Could Soon Be Over
7 min read
Robert F. Kennedy Jr. has some thoughts about Ozempic. According to the nominee to run the Department of Health and Human Services, the government should not provide the drug for millions of Americans, but instead address obesity and diabetes by handing out organic food and gym memberships. Like many of RFK’s statements, these ideas have elicited some outrage. Their basic premise, though—that Americans should control their weight by eating better and getting exercise—could not be more mainstream.
But this commonsense philosophy of losing weight, as espoused by RFK, the FDA, and really almost any doctor whom you might have asked at any time in recent memory, has lately fallen out of step with the scientific evidence.
Lifestyle interventions have been central to the nation’s decades-long attempt to curb its rates of chronic illness. Eat less, move more: This advice applies to almost everyone, but for those who have obesity or are overweight—about three-quarters of the adult population in the U.S.—dieting and exercise are understood to be among the most important methods to improve their health. Even now, when doctors have access to Ozempic and related GLP-1 medications, which deliver lasting weight loss and a host of life-extending benefits without the need for surgery, changes to behavior still take precedence. Formal treatment guidelines for obesity have affirmed RFK’s approach, more or less, and argued that “lifestyle therapy remains the cornerstone of treatment.” And according to the government, the drugs themselves are fit for use only “as an adjunct” to a reduced-calorie diet and increased physical activity.
This insistence on the status quo has begun to seem a little strange. It’s long been known that prescribing dieting and exercise simply isn’t that effective as a treatment for obesity. People may slim down enough, at least initially, to prevent or help control type 2 diabetes, said Tom Wadden, an obesity researcher at the University of Pennsylvania who has been involved in clinical trials of both lifestyle modifications and GLP-1 drugs as treatments for obesity. But he told me that amount of weight loss will not reverse sleep apnea or prevent heart attacks or strokes.
For people with severe obesity today, even the modest benefits of dieting and exercise seem moot. Over the past few years, clinical trials of Ozempic and related drugs have shown that the “cornerstone” of treatment adds almost nothing to these medicines’ effects on people’s body weight.
The mere possibility that dieting and exercise no longer matter like they used to has produced its share of awkwardness within the field. “I’m going to answer carefully,” David Saxon, an obesity specialist at the University of Colorado’s Anschutz Medical Campus, said when I brought this up with him last spring. “I don’t want you to quote me saying, ‘He doesn’t think lifestyle is important.’” For older anti-obesity drugs, he said, the evidence in favor of prescribing dieting and exercise first (and in addition) is very clear: In clinical trials, patients who received a lifestyle intervention in addition to the drugs lost twice as much weight as those who didn’t.
But the data tell a different story for the newer drugs, Saxon and other doctors told me. In most of the clinical research on GLP-1s, patients get the medicine in combination with a modest lifestyle intervention: monthly, 15-minute check-ins with a counselor, for example, and advice to cut back on calories and do a couple hours’ worth of exercise, like walking, every week. In one of the large trials of Wegovy, called STEP 1, this approach produced a weight loss among participants of about 15 percent of their body weight. Another trial of Wegovy, called STEP 3, tried something more: Participants were offered biweekly check-ins with a registered dietician, and they spent their first two months on the drug consuming very-low-calorie meal replacements. Evidence suggests that, in the absence of Wegovy, all of this extra coaching would make a major difference to people’s health. But for people on Wegovy, the benefits were negligible: Those enrolled in the STEP 3 trial lost an average of 16 percent of their body weight, just a hair more than the people in STEP 1 lost. “That speaks to the point that maybe the intensive lifestyle program is not necessary with these new medications,” Saxon said.
He’s seen this play out within the Veterans Affairs system, where he also works. Patients on the older, less potent anti-obesity drugs were expected to participate in an ongoing lifestyle-modification program with monthly check-ins, Saxon told me. Now that he and his colleagues are prescribing GLP-1s, “we don’t really mandate that anymore,” he said, “because we see that even without it, people are maintaining their weight loss with these newer meds.” Eduardo Grunvald, the medical director of the weight-management program at UC San Diego Health, told me that he had the same impression. “The bottom line is that you don’t necessarily need intense lifestyle intervention for these drugs,” he said when we spoke in March.
Even so, obesity specialists, including Saxon, haven’t given up on dieting and exercise. But the field has begun to reevaluate the nature of such guidance. “We need to figure out what it’s going to look like,” Sue Yanovski, who co-directs the Office of Obesity Research for the National Institute of Diabetes and Digestive and Kidney Diseases, told me. Since last year, a series of reviews, editorials, and perspective papers, mostly published in obesity journals, have explored this very question. One paper, for instance, argued that instead of aiming to produce a “quantity” of weight loss, obesity specialists should now emphasize its “quality.” A co-author on that paper, the Wake Forest University obesity doctor and epidemiologist Kristina Lewis, told me that GLP-1 drugs don’t make dieting and exercise irrelevant at all; in fact, they free up patients “to focus on lifestyle intervention in a more refined way,” by clearing out cravings and tabling the need for counting calories. People on Ozempic, she said, and their doctors, too, can start to think about switching to a wholesome diet, being more active, getting more sleep. All of these interventions will be beneficial regardless of your weight.
This all sounds very reasonable, but in a broader context, it also feels like a concession. For decades now, the most ardent critics of the weight-loss industry and of its associated doctors have been saying something similar: Healthy behaviors can and should be decoupled from the single-minded goal of making people smaller. Now, ironically, the tenets of this movement, which came to be known as “Health at Every Size,” are being adapted for the treatment of obesity.
But if lifestyle interventions are meant to have the same benefits for people diagnosed with obesity as they would for anyone, how special is their role in treatment? Lewis and other doctors told me that people on Ozempic might still need some tailored dieting and exercise advice, because rapid weight loss can create specific health needs. For instance, clinical trials found that people on GLP-1 drugs were losing lots of muscle and bone as their bodies shrank in size; in fact, these and other fat-free tissues accounted for 25 to 40 percent of their total weight loss. To mitigate any added risk of weakness or fractures that might result, some experts now suggest that people on these medications should eat more protein and engage in more resistance training than they might in a traditional lifestyle intervention.
Advice on muscle-building diets and workouts could end up as part of standard care for people on Ozempic. “On a rational basis, I would say that we should be doing this,” Wadden, who was a member of the research team for the STEP 1 and STEP 3 trials, told me. Still, he acknowledged that the evidence for this approach isn’t yet complete. Wadden has been studying lifestyle interventions for people with obesity for decades. Some of that work found that adding resistance training and aerobic exercise to very strict diets did nothing to prevent the disappearance of lean body mass. The people who did these workouts were “really swimming against the current” of the effects of rapid weight loss, he told me. Other obesity researchers have contested the very idea that muscle loss is a problem to begin with. A recent paper from the Journal of the American Medical Association argues that the link between physical frailty and GLP-1 drugs is not supported by the data, and observes that if more than half the weight someone on Ozempic sheds is fat, then they’re sure to end up with a higher muscle-to-fat ratio than they had before.
Doctors still don’t fully understand why people on GLP-1s lose so much weight to begin with. Ozempic may be working, on its own, to foster different ways of eating, Wadden told me. “The drug changes your diet dramatically without a lot of conscious effort,” he said. “How does it change? We don’t know.” People on the drug may end up eating less across the board, while sticking to whatever diet they had before: One Pop-Tart for dinner, let’s say, instead of five. (In that case, meetings with a dietician would be very helpful.) But the drugs might also work to shift people’s tastes. “So all of a sudden you like more fruits and vegetables,” Wadden said, “and you like lean proteins.” Similar questions may apply to exercise: The mere fact of losing lots of weight could lead someone to engage in more physical activity, regardless of their access to a gym or time spent with a trainer. The studies that might sort this out haven’t yet been run.
Wadden, like many other doctors, remains convinced that dieting and exercise should continue to be the standard therapy for people who are overweight or who have moderate obesity. But for people with more weight to lose—the tens of millions of Americans whose BMIs are higher than 35, let’s say—he now believes the rules are changing. For this group, he said, “I don’t think lifestyle modification is any longer the cornerstone of obesity treatment.”
