Fat and Healthy? What the Science Says About Longevity and Weight

Fat and Healthy? What the Science Says About Longevity and Weight

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In 2019, the U.S. weight-loss industry was worth $78 billion, which includes diet books, workout plans, meal replacements, diet pills, medical programs (including bariatric surgery), and more. The industry is, by all accounts, enormous—if divided evenly, each American household spends $606 on these products per year. 

In part, the industry is self-sustaining. According to a meta-analysis of 29 weight loss studies, 80% of dieters regain their weight over five years, and most of that weight is regained in the first two. With 36% of Americans actively dieting over the course of a given year, there are guaranteed repeat customers. 

Fat and Healthy?  What the Science Says About Longevity and Weight

Longevity Advice aims to reach as many people from as many walks of life as possible. That means we need to address a significant demographic: people in larger bodies. We’re about to tackle diet and nutrition as a unit on the site, but before diving into it, we need to have a conversation about life extension and adipose tissue. 

Who is fat?

Though body mass index (BMI) categories are famously flawed, it’s the shorthand used in many studies to discuss various weight categories, and I’ll reference them in this article. A BMI over 30 is considered obese. You can calculate your BMI using your height and weight

Body fat is a more accurate measure of excess weight. Men are categorized as obese with 25%+ body fat. Women are categorized as obese with 35%+ body fat. 

Some “obese” individuals, as calculated by BMI, have low body-fat percentages, possibly due to muscle weight, and some normal weight people have high body-fat percentages because of lower muscle mass, hence the shorthand “fat.”

According to a 2014 U.S. study, more than two-thirds of respondents agree with the statement, “one of the worst things that could happen to a person would be for [them] to become obese.” Presumably, there’s a fear of weight stigma, shortened life expectancy, and poorer quality of life. This article aims to examine what the science says about what adipose tissue really does to the body, look at how it affects human life extension, and suggest considerations for larger individuals who are spanners.  

Why is it important to talk about adipose tissue?

We live in a world of fat people.

According to the World Health Organization, 1.9 billion people worldwide are overweight or obese. And about three in four (73%) Americans over the age of 20 are also overweight or obese. 

These people are our mothers and fathers, sisters and brothers, best friends, teachers, colleagues, and ourselves. When talked about as a group, there is a lot of animosity toward fat people, but when brought down to the individual level, it’s important to remember that these are all people whom we want to live for a long time. 

Adipose tissue has an effect on health: that much is clear. We discuss how two sections below.

What determines how much a person weighs?

Adipose tissue. Source

There are three major theories that the scientific community relies on to explain weight regulation: set point theory, settling point theory, and the dual intervention point model. In brief, the theories are as follows: 

  • Set point theory: There are innate biological controls for every individual that regulate weight to a certain predetermined weight. For example, someone who weighs 150 pounds will have trouble gaining or losing 15 pounds in either direction and then be highly unlikely to maintain that new weight. 
  • Settling point theory: From race to socioeconomic status to diet to activity level, weight will “settle” at a weight reflecting all environmental inputs. There is no pre-set range for how much an individual can weigh. For example, someone who weighs 150 pounds will be able to gain or lose 15 pounds by changing their environment and have no difficulty maintaining that weight so long as their environment continues supporting that weight gain or loss. 
  • Dual Intervention Point Model: As a blend between set point and settling point theories, the dual intervention point model argues that there’s a set point “range” for each individual, and that the body will fight against any intervention to keep one’s body weight above or below said range. For example, someone who weighs 150 pounds might have a set point range of 143 to 157 pounds. When gaining or losing 15 pounds, the first seven pounds might be easy to slough off or put on, but after that, the body becomes resistant to the additional eight pounds, and further weight gain or loss is impossible to maintain. 

While things like diet, a sedentary lifestyle, eating frequency, access to healthcare, genetic conditions, medication, socioeconomic standing, childhood trauma, disease, and psychological factors might all contribute to weight gain, no weight regulation model perfectly explains why some people are fat and others aren’t—why most people can’t keep weight off after a period of dieting and yet some can. 

What does adipose tissue have to do with longevity?

Few scientists will argue that adiposity or an obesogenic environment is healthy, but the science about why and how is nuanced. 

For example and counterintuitively, overweight people tend to live longer than normal or underweight individuals. 

A 2013 meta-analysis of 97 studies found that, compared to “normal” weight individuals, people with grades 2 and 3 obesity (BMI of 35+) were significantly associated with increased all-cause mortality. However, grade 1 obesity (BMI of 30 to 35) had no correlation with increased all-cause mortality. Overweight people (BMI of 25 to 30) were associated with “significantly lower all-cause mortality than all the other groups.” Pre-existing health conditions and a history of smoking were controlled for in the study. 

This study is an example of the “obesity paradox,” wherein overweight and grade 1 obese individuals tend to outlive their slimmer and larger peers. For example, these individuals tend to live longer after cardiovascular events when they have coronary artery disease. And another study, covered well by Dr. Josh Mitteldorf (Part 1, Part 2), found that of a group of 5,000 people and their offspring, tracked over 74 years, the people who lived longest were average weight in their youth and gained weight when they were middle-aged. Dr. Mitteldorf explains, “There were not enough people who had actually lost weight to constitute a subgroup, but the group identified as ‘low-normal weight’ all through their lives showed up with 40% higher all-cause mortality than those that gained weight.”

The obesity paradox is, indeed, a paradox. According to the CDC, “Obesity is associated with the leading causes of death in the United States and worldwide, including diabetes, heart disease, stroke, and some types of cancer.” In all my research, I could not find a doctor who would go as far as to advocate for a “normal”-weight person to purposefully accumulate more adipose tissue. And that’s not surprising—given the number of negative health outcomes that correlate with obesity, I would go as far to say that doing so would be unethical. 

Were I to venture a guess, the discussion is really about morbidity versus mortality: fat people might live longer, but they live with more diseases. 

What should fat people who are interested in life extension do? 

fat and healthy obese hiker

Spanners are people who look to indefinitely stretch out their healthspan and lifespan—and given the rate of overweight and obese people in the Western world, there are inevitably lots of fat spanners. Assuming that weight-loss trends continue with a high failure rate, the majority of fat spanners will not be able to lose and maintain their weight loss through diet and exercise. 

Does that mean that fat spanners shouldn’t diet and exercise? Absolutely not. In fact, diet and exercise are arguably more important for fat people interested in life extension. 

Like individuals who test positive for the harmful BRCA gene variants or who have a condition like depression or diabetes, there are some extra steps fat people should consider when it comes to life extension. These steps do not vary significantly from steps for the general population. Remember: most diseases correlated with obesity (diabetes, heart disease, stroke, and cancer) also correlate with age. A fat 30-year-old is still likely to have better health outcomes than a normal-weight 50-year-old in the following 30 years. The goal would be, regardless of weight, for the younger individual to stay biologically young, and for the older individual to stop or reverse biological aging regardless of weight. 

Longevity Advice is entirely dedicated to life extension—you’ll find lots of tips and tricks on this whole site. If you’re fat and this is the only article you will ever read about life extension, consider starting here.

1. Focus on cardiorespiratory fitness

A meta-analysis of normal weight, overweight, and obese fit and unfit individuals used VO2 Max to gauge all-cause mortality in each category. While unfit overweight and obese individuals were at a much higher risk of all-cause mortality, “Overweight and obese-fit individuals had similar mortality risks as normal weight-fit individuals.” The study, along with current WHO guidelines, encourages all adults, regardless of weight, to get at least 150 minutes of moderate-intensity aerobic physical activity per week. Aerobic exercises include biking, swimming, running, hiking, and playing sports. 

2. Strength train

One theory explaining the obesity paradox is that fat people have more muscle—they have more to move around, after all. A 2018 cohort study found that overweight and obese individuals with low muscle mass had a dramatically higher risk of all-cause mortality. But overweight and obese individuals with high muscle mass, again, had similar outcomes to high muscle mass normal-weight participants. Consider using a free strength training app that will plan all your workouts for you. The American Heart Association recommends strength training twice per week

3. Use physical therapy for functional mobility 

Obesity is associated with mobility disability—osteoarthritis, especially, significantly correlates with weight, particularly of the knee and hip. Like with normal-weight adults, physical therapy is a great intervention for mobility problems preventing physical activity. 

4. Talk to your doctor about Metformin

Metformin is a drug commonly prescribed to diabetic patients. It’s controversial within longevity circles—there are studies that have found that Metformin could help with human life extension, but those studies have faced significant scrutiny. Metformin may specifically help fat patients live longer, though there’s variability across age and sex. Berberine may have a similar effect but doesn’t require a prescription.

5. Eat healthily 

I recognize that there are a lot of opinions on what “eating healthy” means and just as many studies to substantiate those claims (and get excited, because we’re going to dive into all of them over the next few weeks!). In general, a diet rich in whole grains, vegetables, fruits, nuts, and fish is correlated with lower all-cause mortality, whereas diets with high red and processed meat correlate with increased all-cause mortality. 

6. Normalize fit, long-lived fat bodies

Did you know that the world’s fattest marathoner was a man who weighed 427 pounds? The fattest female marathoner weighed 346 pounds, for those curious. I think that one of the biggest hurdles fat people face is that there isn’t much in the way of role models unless you go out of your way looking for them (I mean, just look at how fat people are portrayed on TV—and how even physicians buy into those biases to the detriment of their patients). Emphasize media that portrays fat people as go-getters and accomplished athletes. See yourself in people who look like you.

None of these interventions guarantee weight loss. However, they may lead to longer, healthier lives for fat spanners. Instead of cycling through weight loss programs, consider these interventions for longevity instead. 

What else is there to say about being fat and living a long time?

Obesity paradox for living a long time

This article didn’t have quite enough space to include some nuances about fat and longevity, including studies on the waist-to-hip ratio, visceral versus subcutaneous fat, brown versus white fat, and the controversy over whether it’s possible to be fat but fit. It also omitted to mention the Health at Every Size (HAES) movement, which one could argue would be essential for an article like this. However, because this article medicalizes obesity, it wouldn’t fit into a HAES framework. Finally, I didn’t take the time to go through how systemic biases against fat people may cause higher rates of morbidity. There isn’t a lot of concrete evidence on the subject, though I do find it a compelling argument. 

What do you think? Is there space for fat individuals in the life extension community? Which interventions would you recommend, and which would you leave behind? I look forward to reading your comments.


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  4. Matthew Barnett

    > Were I to venture a guess, the discussion is really about morbidity versus mortality: fat people might live longer, but they live with more diseases.

    Another explanation is that these studies are plagued with methodological issues related to reverse causality. Chronic diseases, smoking, and some other addictive drugs often cause people to lose weight. So if you just look at people who are low weight, or have lost weight since early adulthood, you might not get an accurate sense of the longevity benefits of losing weight on purpose through dieting. A good review article that expands on this argument is _Optimal body weight for health and longevity: bridging basic, clinical, and population research_ by Luigi Fontana and Frank B Hu.

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