Can Being Thin Ever Cause Heart Attack or Disease?

So many heart disease victims are thin; but is this because so many variables can damage the heart, or is underweight a risk just like obesity is?

Well first, we all know that slim, slender, thin and skinny people can get heart disease as well as suffer a heart attack.

So can people with baldness, hearing impairment, short stature and blue eyes.

A coinciding physical feature or condition doesn’t mean cause and effect. 

So when a person with a lean build suffers a heart attack or is told they have severe blockages in their coronary arteries, we can’t just attribute that to their body weight.

However, if they weigh 300 pounds, it’s mighty tempting to blame the weight.

Likewise, if that thin individual has been smoking two packs a day for 20 years, it’s easy to blame the smoking on the heart attack as well.

Heart problems don’t only happen to overweight people. And they don’t only happen to smokers.

But the deeper question can be tricky: Can being naturally thin, by itself, cause heart disease or a heart attack in someone who is otherwise healthy, who doesn’t smoke, who has normal blood pressure and even exercises?

These days the word “thin” gets tossed around a lot.

• Generations ago it referred to someone from a developing country with a visibly malnourished body.
• It was also once used to refer to the body in someone with anorexia nervosa.

Today, it’s regularly used to describe a woman’s body that fits into a size 8 pair of jeans, or a man who is merely not overweight.

That’s why it’s better to use terms such as slender, slim, trim, lean and even non-overweight.

Back to that tricky question: Excluding those with anorexia nervosa (who aren’t healthy anyways, due to the damage that their severe malnourishment does to their health), the evidence does not clearly show that healthy “thinness” alone causes heart attacks, coronary artery blockages or chronic heart failure.

What the Research Says About BMI and Heart Health

Some research shows that underweight or low BMI can be associated with higher cardiovascular risk.

A large cross‑sectional analysis of nearly half a million U.S. adults by Donghwi Park, Jong-Hak Lee and Seungwoo Han in 2013 found that people with a BMI under 18.5 had about a 19.7% greater risk of cardiovascular disease than normal-weight adults.

What studies such as these don’t probe is why those individuals are underweight.

There could be an underlying medical reason that somehow causes a smaller appetite or less muscle mass while also leading to cardiovascular risk.

On the other hand, long-term population-based studies consistently show that overweight and obesity carry the clearest and strongest increased risk of heart disease.

A 2018 study (Khan et al) in JAMA Cardiology followed a large cohort over many years and concluded that lifetime risk of cardiovascular disease rose substantially with higher BMI.

Similarly, the Million Women Study in BMC Medicine found that new coronary heart disease risk increased progressively with BMI.

The grey area with BMI is between 25 and 29, which is not obese, but overweight.

People with more muscle mass than average can find themselves in this category, since BMI uses only height and weight for calculation; it doesn’t use body composition.

These athletic individuals have higher BMI’s but normal to low body fat levels.

The bottom line is that while low BMI might in some data show slightly elevated risk in certain contexts, being overweight or obese is the more consistent risk factor for heart disease.

Studies in Low BMI Patients With Heart Disease

Some studies in people who already have coronary artery disease show that low BMI is associated with worse outcomes.

A 2012 meta-analysis (Wang et al) of over 1.3 million CAD patients found that underweight patients had higher short-term and long-term mortality than normal-weight or overweight patients.

So here, we’re looking at people who already have heart disease, which is quite different than the concept of healthy slimness directly leading to heart damage over time.

The STABILITY trial reported that participants with a BMI under 20 had more than double the risk of death, cardiovascular death and heart failure compared with those in the 25-29.9 BMI range.

But again, these findings apply to people who already have heart disease, and plus, the comparison group was in the overweight BMI range, rather than obese. Many could’ve been athletes with more muscle that inflated their BMI.

• Low BMI in these cases may reflect frailty, prior weight loss, poor nutrition or other underlying conditions.
• These factors likely drive higher risk, rather than the low body weight being to blame.

Why Being Trim, by Itself, Is Hard to Pin As a Cause

The rudimentary tool of BMI can’t read the amount of muscle vs. fat in any given individual.

The area is greyist between 25 and 29, give or take a few points in either direction.

Certainly, we can confidently conclude that someone with a BMI of 16 is abnormally low in both fat and muscle, and someone with a BMI of 45 has abnormally high body fat (though they can also have higher muscle mass due to weightlifting).

It can’t be stated too much that two women of same age, height and weight could have entirely different body compositions but both have a BMI of 20.

Many studies showing higher risk in low-BMI groups do not separate out those differences.

Low BMI often coincides with other risk factors: poor nutrition, low muscle mass, chronic illness and older age.

For example, a long-term cohort study by Aune et al., published in BMC Public Health in 2014, found that higher all-cause mortality in underweight participants was largely driven by external causes, not cardiovascular disease.

What This Means for Healthy, Slim People

If you’re lean or slender but otherwise healthy with nutritious eating habits, normal blood pressure and cholesterol, and you exercise and don’t smoke or drink, there is no hard evidence that your “thinness” alone increases heart disease risk compared with a heavier person.

Being slim doesn’t guarantee protection, but it also doesn’t guarantee risk.

For instance, a slim individual who smokes, doesn’t exercise and has a high sodium diet already has three strikes against him as far as cardiovascular disease risk including stroke.

If this same man gained a 120 pounds over the next three years, this obesity would be a fourth — and a very big fourth — risk factor for heart disease or attack.

If he quit smoking, cut down on sodium and exercised at least 150 minutes a week — but still kept on the new 120 pounds — this obesity would still be a glaring risk factor for cardiovascular disease.

• Obesity is an independent risk factor for heart attack, clogged arteries and stroke!
• Slimness, as just described, has not been proven in any way to be a risk factor.

Family history is an uncontrollable risk factor, but so many risks can be modified such as better stress management, a high fiber intake and healthy sleeping habits.

When you read on social media, “Being fat doesn’t cause illness because skinny people get sick too!” you absolutely must never take this seriously.

It’s like saying, “Smoking can’t cause illness because nonsmokers get sick.”

 

Lorra Garrick is a former personal trainer certified by the American Council on Exercise. At Bally Total Fitness, where she was also a group fitness instructor, she trained clients of all ages and abilities for fat loss and maintaining it, muscle and strength building, fitness, and improved cardiovascular and overall health. 

Top image: Freepik