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This story mentions weight, weight loss, and/or prescription GLP-1 drugs, which are FDA-approved for weight management in adults diagnosed with obesity or with overweight and at least one weight-related health condition. Recently, these medications have become extremely popular, in part due to offlabel use. At SELF, our job is to present you—our reader—with science-backed information that you can use to guide the decisions you make about your body, which is why we wrote the article below.
While research suggests having a higher weight may increase your risk for certain conditions, people can be healthy at every size. The categorizations of obesity and overweight can contribute to weight stigma, and they are often based on body mass index (BMI), which is not an accurate measure of health. For some people, pursuing weight loss can be harmful, for instance by leading to weight cycling or increasing the risk of developing an eating disorder; for others, it may be helpful for addressing health concerns or simply having an easier time existing in a world with rampant anti-fat bias. These conversations require nuance, and we hope to provide it. Before taking any medication or making decisions about your health, talk to your doctor or a health care professional.
Decades of research and news articles espousing an “obesity epidemic” and tons of weight loss products launched under the guise of wellness have contributed to a deep-seated misconception: that weight and health always go hand-in-hand. This concept has fueled unrealistic body standards and fomented weight stigma in doctor’s offices, which can worsen the quality of care people in large bodies receive. In reality, the two have a flimsier tie—one that doesn’t hold for 100% of people all the time.
Yes, research suggests having a higher weight can be associated with a range of negative health outcomes, including type 2 diabetes, heart disease, and 13 types of cancer. And in certain cases, studies have uncovered potential mechanisms behind those connections. But correlation is not causation: Not everyone who fits a particular size parameter goes on to develop these issues, and plenty of people in large bodies live long, healthy lives. (Factors like race and socioeconomic status can also drive what appear to be clear links between weight and health.) For that reason, many fat people find the terms overweight and obesity—defined by the World Health Organization as “abnormal or excessive fat accumulation that presents a risk to health”—to be quite problematic, as they inherently pathologize all fatness.
In January 2025, The Lancet Diabetes & Endocrinology published a Commission on obesity reflecting the consensus of 58 international experts led by Francesco Rubino, MD, chair of bariatric and metabolic surgery at King’s College London. What they found is that obesity indeed has no singular manifestation. Carrying weight and losing weight affect different people in distinct ways that may or may not influence their health now or down the line. We spoke with several experts and physicians who study or specialize in weight management to break down this nuanced topic.
Much of the research on weight is based on body mass index…which is a crappy measure of health or illness.
BMI is a basic snapshot of body size calculated by dividing a person’s weight in kilograms by their height in meters squared, which sorts people into the boxes of “underweight” (any number less than 18.5), “healthy weight” (between 18.5 and 24.9), “overweight” (from 25 to 29.9), and “obese” (30 and over). These classifications are convenient fodder for research: Scientists can track health risks linked with weight by assessing how large groups of people in each bucket fare over time. BMI’s simplicity has also given it staying power in doctor’s offices and made it a part of the prescribing criteria for weight-loss treatments.
But we’ve known for quite some time that it’s a crude proxy for the health of any one individual—which makes sense, since it’s assessing mass alone and not what that mass is made up of (say, fat versus muscle versus bone) or how well it’s functioning. Study after study has pointed out that BMI alone doesn’t exactly track with health metrics or risk of death; people with high BMIs can be healthy just as folks with “normal” BMIs can be unhealthy. The tool’s limitations spring partly from the fact that it was created using white men, who may have different patterns of fat distribution than people of another sex or ethnicity. It’s the reason BMI is known to overestimate risk in Black folks and underestimate it in Asian people. And since it doesn’t account for body composition, it fails in people with lots of muscle too. Case in point: Olympic medalist Ilona Maher and her overweight BMI of 29.3.
Other physical metrics may be a bit better (though still not perfect) at assessing weight-related health risks.
To get around BMI’s limitations, doctors have turned to more precise measures to assess body size and fat—like fancy scans that show your percentage of fat relative to your weight and simpler measures like waist circumference as well as waist-to-hip and waist-to-height ratios, which are especially suggestive of fat mass. Having a high number on any of these metrics is a stronger indicator of your risk for developing a health issue than purely BMI. But the key word there is risk. “Having a higher risk doesn’t mean that that person will wind up with this problem for sure or that they have any problem here and now,” Dr. Rubino tells SELF.
For this reason, it’s often required to be diagnosed with a disease linked with obesity (say, type 2 diabetes or high blood pressure), typically called a comorbidity, to be prescribed or get insurance coverage for weight-related treatments. (Note that the word comorbidity is problematic for implying that weight is always the first, well, morbidity.) But as the Lancet commission points out, this focus on other conditions suggests that a certain amount of fat alone can’t trigger symptoms worthy of care…when we know that in some folks and in certain scenarios, it can (more on this below). So while these efforts beyond BMI have helped more accurately pinpoint obesity and the folks at risk of its potential fallout, they still won’t tell you if a specific weight or amount of body fat is currently problematic for your health.
So is obesity a disease?
It’s a question that’s been hotly debated for years, not just on medical grounds, but from a cultural standpoint too, given that any conceptualization of weight exists in the messed-up societal context of shame and stigma.
On the medical side, part of the controversy stems from what researchers have identified as the “obesity paradox”: Despite being correlated with developing a bevy of diseases, obesity is sometimes associated with a reduced risk of dying from those conditions. Part of that apparent paradox can likely be explained by the BMI issue: Some of the folks with higher BMIs who outlived their “normal” BMI counterparts might not have had much extra fat at all (think of muscular folks), while people with lower BMIs who died sooner could’ve had excess fat and very little lean tissue. Indeed, measuring body fat versus BMI erased what had appeared to be a survival benefit of obesity in a study on heart failure. But still, there’s some evidence that folks with a higher relative BMI can fare as well, if not better, than those with a lower one, particularly in studies on heart attack, hip fractures, and infectious diseases.
Aiming to make sense of these conflicting insights, the Lancet commission determined that obesity can likely exist in two ways: as a disease (which they call clinical obesity), when the fat itself appears to cause a sign or symptom of organ dysfunction or a negative impact on day-to-day functioning, or simply as a physical trait and potential risk factor when the fat isn’t having any current negative influence on a person’s health or quality of life (preclinical obesity). This doesn’t mean preclinical obesity will always turn into clinical: Perhaps the type or location of your fat just isn’t harmful, or despite being more susceptible you don’t encounter the trigger that sets you over the edge, Dr. Rubino says. (More fat can also be a sign of a distinct disease, like hypothyroidism, or a medication side effect.) All to say, the Lancet breakdown makes clear that “obesity,” as described by a certain BMI or amount of fat, does not always have medical consequences.
That leaves the cultural piece of the controversy. Recently, the medical establishment has adopted the obesity-is-a-disease message in part to get across that fatness isn’t the result of poor choices, laziness, or neglect. But of course a blanket designation of obesity as an illness unfairly pathologizes all large bodies. At the same time, the opposing sentiment that obesity is never a disease may delegitimize its potential health impact and alienate those who seek care for it. What’s more important to undoing both forms of stigma than labeling it a disease or not, Dr. Rubino contends, is knowing that regardless of how it does (or doesn’t) affect health, weight is controlled largely by biology, not willpower.
It’s helpful to think of body weight regulation like body temperature regulation, Dr. Rubino says. Some extent of it may be within your control, just like you can change your environment to make your body feel cooler or hotter. But you also can’t just reset your internal thermostat or chill yourself out of a fever at will, and the same goes for weight: There are many factors that influence body size, many of which you can’t simply alter because you want to (more on this later). And just like temperature, weight could be a relevant health datapoint—but also may not tell you much in and of itself.
Here’s how researchers think having a larger amount of fat may potentially harm your health now and up your risk for issues in the future.
The reason why there’s no straight line between a high fat level and health problems is because not all fat has the same effect among different people or even in one person. Where it’s located, how it’s functioning—because fat isn’t just a passive source of stored energy but a bioactive organ too—and whether it’s influencing other body processes or even your mental state can all determine its health impact or lack thereof. Here, you’ll find a breakdown of the routes through which having more body fat might affect health.
When you eat food, your body burns some of that fuel right away to keep your core systems chugging along and stores what it doesn’t use immediately in fat cells that grow to accommodate it. Exactly where your body puts it, however, can influence its effects: Initially, most of it goes just below your skin, in subcutaneous tissue (like in your arms, hips, and thighs), which is a “safe, protected” place, Maren Laughlin, PhD, codirector of the NIDDK Office of Obesity Research, tells SELF, as it stays calm and out of the way. But at a certain point, those areas can become overfilled, leading your body to stow anything additional as visceral fat, which is lodged deep in your belly and is more metabolically active and risky. (Factors including genetics, hormones, age, and even having had a low weight at birth can make you more likely to store fat viscerally, as can being of Asian descent or having given birth or gone through menopause; while research suggests exercise might help you tuck more fat below your skin.)
Visceral fat cells are basically chaotic: They aren’t designed to store lots of fat for a long time, Dr. Laughlin explains, and they tend to spill some into nearby organs like your liver, heart, pancreas, and skeletal muscle (which don’t normally hold fat). The ballooning visceral fat cells along with the fat in your organs can then release chemicals that set off alarm bells for your immune system, triggering a chronic state of inflammation—which ups your risk for conditions like heart disease, type 2 diabetes, and cancer. Bombarded by fatty trespassers and inflammation, your organ tissues may struggle to recognize and respond to insulin, the hormone that prompts them to metabolize sugar. To compensate, “your pancreas will work over time to pump out more insulin,” Dr. Jensen says. But “we aren’t born with infinite pancreatic capacity,” he says, so eventually, there may not be enough to get your cells to process sugar, leaving too much of it in your blood and raising your risk for type 2 diabetes. (If you have ovaries, the extra insulin could also increase your risk for or worsen symptoms of polycystic ovary syndrome (PCOS), which could impair your fertility.)
The visceral-fat-to-liver-fat pipeline, in particular, may also have an effect on your cholesterol: When your liver is overrun by fatty molecules, it creates more of a certain type of fat called triglycerides that it sends into your bloodstream, which lowers your “good” HDL cholesterol levels, Dr. Jensen says. The resulting change in lipids could lead to plaque buildup in your arteries, worsening your chances of a heart attack or stroke. Separately, with a bigger body, your heart may have to work harder to pump blood throughout it, which may increase your blood pressure and amplify these cardiovascular risks.
Remember how we said fat was bioactive? Well, that’s not just about visceral fat getting inflamed and leaky. Both visceral and subcutaneous fats also contain the enzyme aromatase, which converts androgens like testosterone into estrogen. A surplus of fat could then leave you with extra-high estrogen levels, which are linked to greater risk of cancers like breast, endometrial, and ovarian—though the link with breast cancer is only significant in postmenopausal folks for reasons that aren’t totally clear. It may be that, at this time in life, “your body’s overall tolerance for estrogen is lower,” since your ovaries no longer make it, Arif Kamal, MD, MBA, chief patient officer for the American Cancer Society, tells SELF.
Another fat-created hormone called leptin can cause cells to grow or proliferate in wonky ways (which could spur tumor development), as can insulin, Dr. Kamal adds, which may be elevated in fat people because of the metabolic changes described above.
The mass and volume of fat may pose an outsize burden on certain parts of your body, like, for instance, your joints. Over time, paired with the rise in inflammation noted above, the additional pressure could wear away at the squishy cartilage cushioning your bones, raising your risk for a type of arthritis called osteoarthritis (which can bring joint pain and stiffness)—research suggests people who are categorized as having obesity (per BMI) are more likely to experience knee osteoarthritis, in particular.
Your respiratory system might also bear the physical brunt. Specifically, fat around your neck could push on your upper airway and make it tougher to breathe at night, elevating your risk for sleep apnea (a condition in which breathing repeatedly stops and starts as you snooze). And the presence of belly fat could interfere with the movements of your diaphragm that are necessary to breathe well, making it more likely that you wind up breathless, especially during physical activity or when you have a respiratory infection.
It’s also possible that carrying a certain amount of fat could affect your stability and balance, perhaps putting you at higher risk of falls or simply making it tougher for you to do everyday self-care tasks (though of course that’s not true for all fat people).
Research has repeatedly shown that people in larger bodies—regardless of their BMI, body-fat status, or health—face a mountain of discrimination in many settings, from the courtroom to the workplace to the doctor’s office. This cruel onslaught can damage your mental health, worsening your body image and self-esteem in ways that could raise your risk for or pile onto symptoms of depression. This kind of mental state could in turn lead to behaviors that fuel obesity, for instance if you process shame via emotional eating, Angela Fitch, MD, chief medical officer at weight-inclusive health care company Knownwell, tells SELF. Hence why obesity and depression can become a vicious cycle.
As mentioned, anti-fat bias in medical settings is also proven to negatively impact care outcomes. Doctors may be prone to focus on a patient’s weight at the cost of missing a current medical issue necessitating treatment; research suggests fat people are less likely to be prescribed certain medications. There’s also the fact that medical equipment, exam tables, and gowns may not accommodate folks of a certain size, and drug dosages and recommendations aren’t often designed for larger bodies. (Head this way for our guide to finding a fat-friendly doctor.)
Dr. Fitch also points out that the psychological stress of weight stigma itself can spark an inflammatory response in your body, upping your susceptibility to inflammation-based conditions. Considering all these harms of anti-fat discrimination, it’s very possible that the negative impact of weight might come as much from the mentally taxing reality of being fat in our society as it does the fat itself.
Despite the health risks of having a higher weight, losing weight is far from a panacea. In fact, for some people it can have negative repercussions.
Our cultural tendency to prop up weight loss as the main health goal for people in large bodies has caused more harm than good. When doctors push cutting pounds as a cure-all, patients may not get adequate treatment or may be disincentivized to return for followups, and when society celebrates people for getting thin in all contexts, it plays up the stigmatizing, inaccurate message that any weight loss is good—when of course dropping weight can worsen your health (e.g., if you’re low on nutrients) or be the result of illness.
The truth is, there’s no straight line between pounds lost and health gained. While fat people are, statistically speaking, at higher risk for certain diseases than thinner folks, losing weight might not level the playing field. Indeed, studies show weight loss doesn’t consistently lower mortality for people who are classified as having overweight or obesity (per BMI). On the contrary, pursuing intentional weight loss can actually be harmful, as it may trigger weight cycling (or ping-ponging between high and low weights), which can put stress on your cardiovascular system and increase your risk for depressive symptoms, or make you more susceptible to developing an eating disorder.
Where the research does suggest some positives of weight loss is primarily in folks experiencing symptoms that may be linked to fat or an obesity-related disease. One of the longest-running studies on weight and diabetes risk, the Diabetes Prevention Program (DPP), found that among those at high risk for developing type 2 diabetes, people who lost 5 to 7% of their body weight via lifestyle changes reduced their risk of winding up with the condition by 58% in three years. The large Look AHEAD trial found that people with type 2 diabetes and either overweight or obesity (per BMI) who lost roughly 9% of their weight thanks to lifestyle changes experienced improvements on several metabolic metrics like blood sugar and cholesterol (though it’s worth noting they were not ultimately any less likely to have a heart attack or stroke). And research also suggests both lifestyle- and medication-driven weight loss can ease symptoms of sleep apnea and osteoarthritis.
It’s important to note, though, that in many of these scenarios, positive lifestyle behaviors themselves likely play a role in improving health markers too. (Meaning, weight loss may not deserve all the credit.) In fact, plenty of research has shown that both exercise and diet can better your numbers on a handful of cardiometabolic measures, independent of any fat loss. And even though physical activity by itself has been shown to be less effective for shedding pounds, research shows it could offer powerful support for your heart and slash your mortality—no weight loss necessary.
Weight loss is notoriously hard to sustain—and focusing on healthy behaviors may be a better tack.
The big, glaring reason why we can’t say with certainty that lifestyle-driven weight loss will improve your health long-term is because…we don’t have much data on people actually doing that and maintaining the 5% weight loss often deemed necessary for clinical effects. (A 2024 review suggests even lesser levels of weight loss could be health-positive, but again, some of the benefits might be traced more to lifestyle changes than these minor losses.) As many as 80 to 95% of people who lose substantial weight gain it back.
The reasons why are complex. A part of it comes back to the temperature metaphor: Much of weight regulation happens in a part of your brain called the hypothalamus, which controls automatic body functions. Just as it receives temperature-related signals from your body—and drives behaviors like sweating and shivering to keep things in check—it also takes cues from your stomach and pancreas to influence how hungry or full you feel, Caissa Troutman, MD, a board-certified family, obesity, and culinary medicine specialist and spokesperson for the Obesity Medicine Association, tells SELF. Over time, it’s thought that the hypothalamus, along with other brain regions, develops a “set point” for your weight. And when you dip below that, your brain essentially revs up the signals to bump you back to that equilibrium, spiking hunger hormones and decreasing satiety ones, Dr. Troutman says. For the same reason, your brain also tells your body to expend less energy than it did before, Dr. Laughlin says. Evolutionarily, this kind of rejiggering, or adaptation, would’ve helped prevent starvation, Dr. Fitch points out. But these days, if you’re trying to cut fat, it may make it super difficult, if not impossible, to keep it off through diet and exercise alone.
On top of that, there are the environmental factors—living in a culture where less-healthy foods are accessible, cheap, and so palatable they may be addictive. Like all other animals, we respond to our surroundings, Dr. Laughlin says. “There’s something about a food-rich environment that puts our brains on high alert for finding and consuming it.” Hence the inaccuracy of pinning weight loss on willpower and the reason we don’t know if it’s beneficial (or even possible) to achieve long-term weight loss via lifestyle.
That’s where the role of prescription weight loss drugs, including GLP-1s, can come into play. The GLP-1s mimic a natural hormone to not only stimulate the release of insulin (which is why they were initially approved for type 2 diabetes) but also tamp down on appetite and increase fullness. In turn, they may lower some of the real biological barriers that otherwise interfere with sticking to a healthy eating plan, Dr. Troutman explains. (Again, we’re talking about biology; the narrative that taking one of these drugs is “cheating” or “the easy way out” springs from the false and damaging sentiment that weight is a matter of willpower.) Scientists also suspect GLP-1s act on parts of the brain involved in reward, which could explain why people desire food less while on them.
Together, these mechanisms may explain why GLP-1s appear to trigger a substantial 12 to 18% weight loss on average. Research points to their potential health benefits too, like lower cholesterol, better blood-sugar control, and less risk of heart attack—which in some cases, appears to happen independently of weight loss. However, evidence suggests you may need to stay on the drugs to keep weight off, likely indefinitely (because of the complex biology that controls our weight “set point”)—and that may not be safe, given limited research on continued use. It’s also worth mentioning, some people report rough side effects like nausea, vomiting, and diarrhea while taking these drugs (and research suggests possible risks of kidney and pancreas complications in rare cases), posing another huge barrier to staying on them long-term. And their sky-high cost is yet another challenge here, complicated by the fact that cheaper compounded options will soon be unavailable.
Weighing these pros and cons of GLP-1s with your doctor can help you figure out if one is right for you. And the same goes for pursuing long-term weight loss more broadly: Depending on your health and lifestyle, it might be a part of your wellness journey. It’s also completely valid to pursue weight loss as a means of avoiding pervasive anti-fat stigma. But given the difficulties inherent to sustained weight loss and the questions surrounding its efficacy, it may be more helpful to focus on eating a well-rounded diet and moving your body in ways that feel good—habits that can seriously improve your well-being whether or not they change your size. Whichever route you take, remember this: Your physical form is never a measure of your morality, success, or worthiness as a person.
