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What Are the Risk Factors for a High BMI?

What Are the Risk Factors for a High BMI?
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Updated on January 29, 2025
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BMI — or body mass index — is a measure of your relative height and weight. The calculation places people into one of several categories: below 18.5 is considered underweight; 18.5 to 24.9 is normal or healthy weight; 25.0 to 29.9 is overweight; and 30.0 and above is obesity.

A high BMI is associated with an increased risk for a number of conditions, including heart disease, stroke, type 2 diabetes, and several types of cancer. A range of factors may put you at risk for a higher BMI, many of which you can change to work toward a healthier weight.

Risk Factors for a High BMI

The reasons someone may become overweight or develop obesity are multifactorial.

 The following are some of the factors.

Genetics

Research suggests that some peoples’ genes put them at a greater risk of a high BMI.

 But genetics usually aren’t the only cause. “If you have parents who are overweight, you’re more likely to be overweight, but this may also be due to lifestyle factors,” says Charlie Seltzer, MD, a weight loss specialist in private practice in Philadelphia.

A Suboptimal Diet and Physical Inactivity

While your genetic makeup is out of your control, two risk factors that you can change are diet quality and physical activity. A diet high in calories and low in important nutrients, in addition to a lack of exercise, can cause gradual weight gain and a higher BMI.

“Maybe you don’t notice that you gained five pounds over the holiday season; the weight continues to come on, and suddenly you’re up by 30 pounds,” Dr. Seltzer says.

Environmental Factors

Do you have bike lanes on your street? Are there sidewalks so you can walk safely? Research has found that these neighborhood features can nudge you into living a more active life, and they may not be factors that you can control.

 Other environmental influences include access to healthy food and high quality grocery stores,

 public transportation in your area, neighborhood safety, and availability of outdoor recreation facilities.

Certain Medications

Some drugs, like those for sleep, blood pressure, and psychiatric conditions, can stimulate your appetite, says Seltzer.

 Others like some heart medications may make you feel sleepy or short of breath, possibly causing you to be less likely to work out or be active.

Some Medical Conditions

Prader-Willi syndrome and Cushing’s syndrome are two examples of medical conditions that cause weight gain or make it more difficult to lose weight.

Why BMI Matters

Overweight and obesity are linked with a higher risk of heart disease, stroke, high blood pressure, high cholesterol, type 2 diabetes, depression, and anxiety.

 A high BMI could also be linked with an elevated risk of certain types of cancer, an often underrecognized relationship, says Seltzer. Higher amounts of body fat are associated with endometrial, esophageal, liver, kidney, pancreatic, colorectal, breast, ovarian, and thyroid cancers, among other types.

An elevated BMI may also affect brain health. One large cross-sectional study found that participants with a BMI of over 30 (falling into the obesity category), had smaller brain gray matter volumes and other structural differences than a group of adults without obesity.

 These are possible markers of cognitive decline.
Then there’s how obesity can affect your day-to-day quality of life. “It can lead to a poor quality of sleep, which makes you tired, negatively impacts healthy habits, and makes people more overweight,” says Seltzer. Research has also linked obstructive sleep apnea, a common sleep disorder that causes tiredness and is associated with various health conditions — including an increased risk of heart disease and mental health issues — with obesity.

Why BMI Is a Flawed Measure

In 2023, the American Medical Association (AMA) adopted a new policy urging physicians not to rely on BMI alone to diagnose obesity.

That’s because BMI is not a perfect measurement and has a number of flaws. BMI does not distinguish the composition of the weight — whether it's made up of fat, muscle, or bone mass — and it doesn’t account for where the fat is found on the body.

 Because of this, a person can have a normal BMI but have low muscle and a lot of fat, which is an unhealthy state to be in. Alternatively, an athlete with much more muscle mass than fat can fall into a high BMI range because of weight.

Additionally, BMI was invented two centuries ago and is based on data from European white men. It doesn’t account for body differences between men and women or among people of different ethnicities, which means its results can be skewed.

For example, research has found that non-Hispanic Black men and women have higher muscle mass and lower body fat percentages than non-Hispanic white people.

 Conversely, people of Asian descent tend to have higher body fat percentages than white people at the same BMI.

 This means individuals can be misclassified as healthy or unhealthy based on BMI alone. To counter this, the AMA advises measuring both BMI and waist circumference — which some researchers have proposed is a simpler, more accurate measure of health risk than BMI

 — to better predict early warning signs of weight-related disease.

How to Reduce Your BMI

If you’re looking to lose weight and lower your BMI, small and sustainable changes can make a big difference in your chance of success. While everyone is different, a well-rounded healthcare team — complete with a mental health care specialist, a registered dietitian-nutritionist, and a primary care doctor, as well as any specialists — may be critical for meeting your individual goals. That said, here are some recommendations for your personal role in weight management.

Keep a Food Journal

You may think you have a handle on your diet habits, but most people don’t actually know what they’re eating, says Seltzer. He recommends tracking what you eat for two weeks. Either a smartphone app or paper notebook will work. Often, you’ll see that there are random bites of food here or there that may add up to hundreds of extra calories each day. It’s these small things that often matter more than your adherence to an of-the-moment diet or whether you eat (or avoid) specific foods or food groups.

One study of 142 participants in an online behavioral weight control intervention found that those who tracked their calorie and fat intake most frequently had the most success. The researchers noted that the habit doesn’t have to be time consuming or tedious. Participants who lost the most weight (about 10 percent of their body weight) spent an average of just 15 minutes per day on their food journal.

Practice Portion Control

Make small and realistic changes to get your calorie count down, Seltzer says. Rather than eliminating foods, just eat smaller portions. That could be ½ cup of ice cream instead of 1 cup. In total, you may end up consuming 5 to 10 percent fewer calories per day, Seltzer notes.

Move Your Body

Both diet and physical activity are important components of weight loss. Exercise requires the body to use more calories for energy, and burning more calories than you consume leads to weight loss.

According to the Centers for Disease Control and Prevention (CDC), most adults need at least 150 minutes of moderate physical activity (such as brisk walking or riding a bike) and two days of muscle training activity (like lifting weights) per week to support physical and mental health.

Look at Your Medication Labels

Specifically, see whether your medication lists weight gain as a side effect. As mentioned, certain drugs can lead to weight gain directly or indirectly. “Most of this can be avoided by keeping an eye on your caloric intake,” says Seltzer.

Your doctor may not always inform you that weight gain is a side effect of a drug you’re being prescribed. Ask about common side effects for any new medication, including weight gain. Knowledge is power!

Get Enough Quality Sleep

When you make sleep a lower priority, you’re setting yourself up for weight gain. “Fatigue raises cortisol [a stress hormone], which acts like an appetite stimulant,” says Seltzer. Lack of sleep can increase your risk of becoming overweight or having obesity because it can lead to dysfunctional eating, less motivation to be physically active, and metabolic changes, according to research.

 Try to snooze for seven to nine hours a night, as the CDC recommends.

Find Ways to Manage Stress

Stress releases cortisol, which puts your body in fight-or-flight mode, raising both blood pressure and insulin.

 As a result, you may crave sugary and fatty foods. Studies have shown that chronic stress is associated with extra pounds around the waist and obesity over time.

Stress-reduction strategies like a quick run, meditation, or a chat with a friend can help calm you down when you feel anxiety rising.

The Takeaway

  • While it's not a perfect measurement, a high BMI is associated with an increased risk for a number of chronic diseases, including heart disease, stroke, type 2 diabetes, and several types of cancer.
  • An array of factors — some of which you can control and others you can’t — may increase your risk for a high BMI, including genetics, lifestyle choices like diet and exercise, your environment, and certain medications and medical conditions.
  • There are steps you can take to lose weight and lower your BMI, including maintaining a healthy diet, exercising, managing stress, and getting enough good-quality sleep.

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Justin Laube, MD

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Justin Laube, MD, is a board-certified integrative and internal medicine physician, a teacher, and a consultant with extensive expertise in integrative health, medical education, and trauma healing.

He graduated with a bachelor's in biology from the University of Wisconsin and a medical degree from the University of Minnesota Medical School. During medical school, he completed a graduate certificate in integrative therapies and healing practices through the Earl E. Bakken Center for Spirituality & Healing. He completed his three-year residency training in internal medicine at the University of California in Los Angeles on the primary care track and a two-year fellowship in integrative East-West primary care at the UCLA Health Center for East-West Medicine.

He is currently taking a multiyear personal and professional sabbatical to explore the relationship between childhood trauma, disease, and the processes of healing. He is developing a clinical practice for patients with complex trauma, as well as for others going through significant life transitions. He is working on a book distilling the insights from his sabbatical, teaching, and leading retreats on trauma, integrative health, mindfulness, and well-being for health professionals, students, and the community.

Previously, Dr. Laube was an assistant clinical professor at the UCLA Health Center for East-West Medicine and the David Geffen School of Medicine at UCLA, where he provided primary care and integrative East-West medical consultations. As part of the faculty, he completed a medical education fellowship and received a certificate in innovation in curriculum design and evaluation. He was the fellowship director at the Center for East-West Medicine and led courses for physician fellows, residents, and medical students.

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