The “fat-but-fit” debate has been around for decades and split public opinion.

The debate revolves around the question of whether those who are overweight or obese yet physically active can be metabolically healthy, despite having excess fat mass.

This debate was recently reignited with a study that called into question the notion that you can be physically fit and have overweight or obesity. It suggested that regardless of physical activity level, having either of the two increased your chronic disease risk (1).

However, critics argue that one study isn’t enough to close the book on the fat-but-fit debate, especially when many feel that the study’s conclusions were overstated.

Due to all of the conflicting information out there, you may wonder what the research really says and whether physical activity can mitigate the health risks that are associated with obesity.

This article explains all you need to know about the fat-but-fit debate, what the research says, and — most importantly — how exercise benefits people of all sizes.

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The fat-but-fit debate has been a contentious topic in the medical and fitness communities for decades.

Kim Yawitz, Registered Dietitian and owner of Two Six Fitness in St. Louis, says the debate “started in 1999 with two large studies that suggested you can be obese and still be healthy (2, 3).”

“The most controversial finding in these studies was that obese men could possibly reduce their risk of dying from heart disease more than threefold with regular exercise, even if they didn’t lose a single pound (2).”

Contrarily, “other studies and public health experts have argued the opposite — that obesity is bad for your health no matter how fit you are.”

Christa Brown, MS, RDN, a weight loss and gut health dietitian, suggests the debate “can be tied into ‘diet culture’ that thin is best and how there is a body positivity movement challenging [this]”.

Brown notes that most research has found strong associations between overweight and obesity (defined as having a body mass index, or BMI, of 25.0–29.9 and 30.0 or over, respectively) and negative health effects, such as chronic disease development (4, 5).

In contrast, individuals with “normal” weight statuses (BMI of 18.9–24.9) tend to have a lower risk of chronic disease. Thus, many experts argue that excess weight is an individual risk factor for poor health (4, 5).

However, the other side argues that most of the research doesn’t look at obesity from all angles, and that there are flaws in their study designs.

In most cases, studies on BMI and chronic disease risk are observational, meaning they examine a snapshot in time and don’t involve an intervention (e.g., dietary changes or physical activity programs). As such, they can’t prove cause-and-effect relationships.

Furthermore, many experts argue that BMI is not a reliable indicator of health, as it fails to consider individual differences such as your sex, fat mass vs. lean muscle mass, and body fat distribution (6, 7).

With both camps having fair arguments and a lack of research to concretely confirm one or the other, the fat-but-fit debate remains a controversial and unresolved topic.

Though news companies ran with bold headlines, such as “Fat but Fit Is a Myth,” and “It’s Impossible to Be Fat but Fit,” the study did not conclude this.

The disputed 2021 study, which analyzed 527,662 people, found that despite being regularly active, those with obesity had two-, four-, and fivefold greater risks of developing diabetes and high cholesterol and blood pressure than people with “normal” weight statuses (1).

Yet, it also observed a reduced risk of chronic disease across all BMI categories in those who were more physically active. The authors concluded that physical activity does, in fact, provide health benefits across all BMI categories in a dose-response manner (1).

What’s more, despite its impressive sample size, it did not measure cardiorespiratory fitness, and the analyses weren’t controlled for diet. Both are major factors in the assessment of heart disease risk (1).

Instead, it relied on self-reported physical activity based on the World Health Organization’s activity guidelines and didn’t consider the type of activity (e.g., 30 minutes of household work would be placed in the same category as a 30 minute, high intensity cycling class) (1).

Without taking into consideration a person’s actual cardiorespiratory fitness and other parameters, it’s difficult to rely on self-reported activity as a true measure of physical fitness (1).

Therefore, while this study provided useful information, it was largely misreported and still leaves many unresolved answers in the fat-but-fit debate.


The fat-but-fit debate argues whether people with overweight or obesity can be physically fit, despite having excess body fat. With valid arguments on both sides, the debate is far from resolved.

Research on obesity and chronic disease is plentiful but very complicated and not fully understood.

Health risks of obesity

Most research finds strong associations between overweight and obesity and negative health effects.

Numerous high quality, robust studies have shown that obesity increases your risk of chronic diseases, such as heart disease, type 2 diabetes, cancer, premature death, breathing difficulties, nonalcoholic fatty liver disease, and mobility issues (8, 9, 10, 11, 12)

For example, one retrospective study including 103,218 people observed a 1.5–2.7-fold greater risk of death among people with obesity, compared with those with “normal” weight statuses (12).

In particular, excess fat stored around the stomach region — known as central obesity — is associated with the most negative health effects, such as cardiovascular disease and metabolic syndrome (13, 14, 15).

However, some individuals with obesity can be metabolically healthy, meaning they have no clinical markers of disease, such as normal blood pressure, cholesterol, and insulin sensitivity. Likewise, a person with average weight can be metabolically unhealthy (16, 17, 18).

Brown recommends “yearly routine physicals and blood work to see what’s going on in the ‘unseen world,’” which may better indicate your overall health.

Physical fitness is more important

One meta-analysis found that individuals with normal, overweight, and obese weight statuses with equal cardiorespiratory fitness levels had the same risk of all-cause mortality. Those who were unfit, regardless of their BMI, had a twofold greater risk of all-cause mortality (19).

These findings suggest that having overweight or obesity doesn’t automatically place a person at a higher risk of health issues. Rather, one’s actual fitness levels — especially cardiorespiratory fitness — appear to play a larger role (19).

Another 30-year follow-up study including 3,307 people showed a 36% decreased risk of heart-disease-related mortality in those that remained physically active. In fact, weight loss provided no additional risk reduction (20).

Many other studies have also shown that physical inactivity is linked to an increased risk of heart disease and early death regardless of BMI. But the good news? Regular physical activity appears to be protective across all weight status categories (20, 21, 22, 23, 24, 25).

That said, while physical activity reduces heart disease risk among those with overweight or obesity, many studies show that their risk is still higher than those of their equally active counterparts with “normal” weight (23, 24, 25).

Research suggests that excess fat mass, especially around the stomach area, leads to increased inflammation that can lead to chronic disease over time. Exercise can mitigate some of this risk by reducing inflammation (28, 29, 30, 31).

However, Yawitz notes, “Given the emphasis on obesity and heart disease, it’s easy to assume that you’re in the clear if you have a healthy body weight. But, that’s not always the case, especially if you’re not very active or have other risk factors.”

Therefore, pursuing physical activity, regardless of your body weight, is beneficial and should be encouraged (28, 32).

But that begs the question: When it comes to the fat-but-fit debate, are we focusing on the wrong thing?


Regardless of your body weight, being physically active can reduce your risk of chronic disease.

“One indisputable fact is that exercise is good for you no matter how much you weigh. Even if it’s true that exercise alone isn’t enough to keep you healthy, it’s a step in the right direction that can motivate you to adopt other healthy behaviors”, says Yawitz.

“The fat-but-fit [debate] needs to consider personalized care and [an] understanding [of] a person’s medical history, genes, environmental influences, and what they are emotionally happy with,” says Brown.

Focusing too much on a person’s weight takes away from other positive actions they’ve taken toward good health, such as increasing physical activity, managing their stress, eating a nutritious diet, and sleeping more.

Brown adds, “If all the boxes are checked and they are at a reduced risk of disease, why should anyone will them into weight loss if they are active regularly?”

Regardless of a person’s weight, everyone can benefit from physical activity. What’s more, making physical activity goals rather than weight loss goals might be easier to achieve (33).

For example, instead of making a goal to lose 20 pounds (9 kg), you could set a goal to walk 30 minutes every day.

Considering the many benefits of exercise, it should be encouraged as a means to promote overall health, not just as a vehicle for weight loss (33).


Instead of focusing on body weight, the emphasis should be placed on increasing physical activity and other healthy lifestyle practices to improve overall health.

Too often, we use aesthetics to gauge physical fitness, but bodies are unique and individual. What fit looks like for one person will most certainly look very different for someone else.

Years of clinical studies have found inconclusive results, and that should be a testament to the notion that everyone is different when it comes to the question, “Can you be fat but fit?”

As with most things, there’s no one-size-fits-all answer. And yes, that pun was intended.

Perhaps, then, we’d be better off assessing physical fitness based on individual markers measured by a trusted physician or personal trainer, rather than judging a person’s health based on looks alone.

From a strictly medical standpoint, physical fitness refers to a person’s ability to perform physical activities (ranging from exercise to daily living activities) using endurance, strength, flexibility, and aerobic capacity (34).

The main markers of physical fitness include (34):

  • cardiorespiratory fitness
  • muscular strength and endurance
  • flexibility
  • body composition

Cardiorespiratory fitness

Cardiorespiratory fitness is one of the most common and widely studied markers of physical fitness. It’s defined as the body’s ability to carry out prolonged exercise using the cardiovascular and respiratory systems (35).

While many laboratory tests measure your cardiorespiratory fitness, an easy way to measure it is to check your resting heart rate, says Yawitz.

“To do this, you’ll find your pulse on your neck, just to the side of your throat. Gently hold two or three fingers to your neck and count the number of times your heart beats as you watch the clock for 15 seconds.”

“Next, you’ll multiply that number by 4. Generally speaking, 60–100 beats per minute is a good target for healthy adults.”

Muscular strength

Muscular strength is also important and involves the muscle’s ability to carry out work against resistance (e.g., lifting, pushing, pulling), while muscular endurance is the muscle’s ability to sustain exercise for a prolonged period of time (35, 36).


Flexibility is the range of movement around a joint. It’s important for preventing injuries and helping with healthy joint movement (35).

Body composition

Finally, body composition refers to the relative amounts of muscle mass, fat mass, water, and bone a person has. While highly individual, more muscle mass is associated with greater physical fitness (35, 37).

Focusing on these parameters to create your fitness goals will be more effective than focusing on your size or weight loss alone.

Most physical activity guidelines recommend getting 150–300 minutes of moderate intensity exercise, or 75–150 minutes of vigorous intensity exercise, each week, with at least 2 days of strength training (38, 39).


Focusing on cardiorespiratory fitness, muscular strength and endurance, flexibility, and body composition can help promote physical fitness.

Body weight is a combination of lean mass (organs, skin, bones, muscle, water, etc.) and fat mass.

In most cases, having a higher fat mass and lower muscle mass is associated with negative health outcomes, rather than body weight itself (40, 41).

While physical inactivity can certainly play a role in fat accumulation, many factors affect one’s weight and body composition, such as (42):

  • diet
  • medications
  • genetics
  • history of dieting
  • age
  • sex
  • sleep
  • stress
  • medical conditions
  • hormone levels
  • mobility issues

Therefore, it’s important to remember that physical activity only plays a small role in a person’s body weight.


Though exercise is important, many other factors affect body weight, including your diet, medications, genes, medical conditions, and other lifestyle factors.

When it comes to fitness, the main goal is to feel your best.

Many benefits of exercise go beyond weight loss or the way your body looks, such as (44, 45, 46, 47):

  • stronger muscles and bones
  • lower risk of injury
  • reduced pain
  • better mood and brain health
  • improved sleep and energy levels
  • increased self-confidence and self-efficacy
  • improved productivity and creativity
  • reduced risk of chronic disease (e.g., heart disease, type 2 diabetes, and cancer)
  • lower risk of early death
  • a healthier immune system
  • a healthier heart
  • better quality of life

Ultimately, exercise provides undeniable benefits to both our physical and mental well-being. Shifting your focus onto this instead of the pursuit of weight loss may make physical activity more enjoyable and sustainable (47).


The benefits of exercise go beyond your body weight. By focusing on other positive benefits of exercise, you may find physical activity more enjoyable and stick to it long term.

Until more conclusive research is available, the fat-but-fit debate will likely continue for many years.

While both sides have valid arguments, focusing on weight is not the answer to good health — and it’s not a strong motivating factor in regards to increasing physical activity.

Regular physical activity provides endless benefits, such as improved mood and mental health, a reduced risk of chronic disease, healthier bones and joints, and better quality of life, for everyone.

Therefore, instead of arguing over which side is right, it’s time we shift the focus onto what truly matters and promote exercise as a means to good health for all.