Peek at your doctor’s chart, and one of the first things you may see is your BMI, front and center. BMI — or body mass index — is a measure of your relative height and weight. The calculation places people into an underweight, normal weight, overweight, or obese category, and may be used as a measure to assess your risk for certain diseases.
Why You Should Care About Your BMI for Your Health
BMI is important. As the Centers for Disease Control and Prevention (CDC) notes, there are four main categories of BMI: 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 obese. (1)
Doctors often apply the measurement on an individual level, but where it is really useful is in population-based research, says Charlie Seltzer, MD, a weight loss specialist in Philadelphia. Dr. Seltzer does not use BMI in assessing his individual patients, because it’s not always useful information.
For example, you can have a normal BMI but have low muscle and a lot of fat, which is an unhealthy state to be in. Or, you can be highly muscular, and thus inaccurately categorized as overweight according to an article published in Sports Health. (2) These are just some of the flaws of BMI.
But it’s through BMI that we know how grave the statistics on obesity really are. About 70 percent of adults are overweight or obese, according to data from the National Health and Nutrition Examination Survey. (3) Likewise, 1 in 6 children and adolescents are considered obese, per the CDC. (4)
A High BMI Can Pose Risks to Your Health
It’s important to know whether you do fall into one of these categories. When you’re overweight or obese, you’re at higher risk for heart disease, stroke, and type 2 diabetes. An elevated risk of certain types of cancer is also vastly under-recognized, says Seltzer. Indeed, the National Cancer Institute notes that higher amounts of body fat are associated with cancers, including endometrial, esophageal, liver, kidney, pancreatic, colorectal, breast, ovarian, and thyroid, among other types. (5)
Another consideration for your future health is how excess body weight is associated with brain health. Indeed, an observational study published in February 2019 in the journal Neurology found that having a BMI over 30 (considered obese) or a higher waist-to-hip ratio (also known as having more belly fat), had lower brain volumes than leaner adults. (6) Brain shrinkage is linked to cognitive decline.
Then there’s how obesity can affect your day-to-day quality of life. “It can also lead to a poor quality of sleep, which makes you tired, destroys healthy habits, and makes people more overweight,” says Seltzer. High blood pressure, high cholesterol, depression, anxiety, and pain are other problems associated with obesity, per the CDC. (7)
What Factors May Put You at Risk for a High BMI?
The reasons why someone becomes overweight or obese are multifactorial, but here are some contributing factors:
- Your Genes Everyone was born with a unique body, and not everyone is designed to be the same. Some people may have a faster metabolism than others, for instance. But there’s a big gray area: “If you have overweight parents, you’re more likely to be overweight, but this may also be due to lifestyle factors,” says Seltzer. (7)
- How You Eat and Move This means how much activity you’re getting in your day and how healthfully you’re eating. “People become obese by consuming more calories than they burn. If you do not [do that], you do not become obese,” says Seltzer. This excess weight can come on rather slowly, maybe even over decades. “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,” he says. (7)
- Your Environment Do you have bike lanes on your street? Are there sidewalks so you can walk safely? These features in your surroundings can nudge you into living a more active life. Other factors, according to Harvard Health: public transportation in your area, neighborhood safety, and a family that supports doing activities together. (8)
- Medication Some drugs, like those for sleep, blood pressure, and psychiatric conditions, can stimulate your appetite, says Seltzer. Others may make you feel sleepy or drowsy, possibly causing you to be less likely to work out or be active. (7)
- Medical Conditions Hypothyroidism, polycystic ovary syndrome (PCOS), and Cushing’s syndrome are a few examples of medical problems that cause weight gain or make it more difficult to lose weight, per past research. (9)
How to Help Reduce Your Risk of Becoming Overweight or Obese
If you’re looking to lose weight and lower your BMI, some small and sustainable changes can actually make the biggest difference in your chance for success.
Take a look at what you’re eating now. 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. 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 adhering to an of-the-moment diet or eating (or avoiding) specific foods or food groups.
In a study pubished in January 2020 in Obesity, which looked at the behaviors and habits of people who lost weight, those who successfully kept it off for more than three years were more likely to set food intake goals, measure their food, and record what they ate compared with a control group. They were also more likely to ignore cravings and practiced making healthy eating choices so that prioritizing nutrition became automatic. (10)
Though conducted by researchers at California Polytechnic State University, the study received a grant from WW, formerly Weight Watchers, a program built on behavioral change. When industry or a specific company directly or indirectly funds a study, there’s always the chance that the results may be skewed in that donor’s favor.
In any case, it’s worth nothing that these are also small habits you may be able to build without a commercial weight loss program.
Make tiny tweaks to eat smaller portions. Make small and realistic changes to get your calorie count down, Seltzer says. (Think drinking one less glass of wine when dining out.) Rather than eliminating foods (even favorite foods), eat smaller portions. That may 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.
See whether your medication lists weight gain as a side effect. As mentioned, certain drugs can lead to weight gain. “Most of this can be avoided by keeping an eye on your caloric intake,” says Seltzer. One problem is that your doctor may not inform you that weight gain is a side effect of a drug she's prescribing. Ask your doctor about common side effects for any new drug, including weight gain. Knowledge is power.
Make sure you get enough 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 lead you to be less motivated to be physically active and more likely to reach for quick and unhealthy food, according to past research. (11) Snooze the recommended seven to nine hours a night for better weight control, recommends the National Sleep Foundation. (12)
Manage your stress levels. Feeling tense not only can make you more likely to reach for unhealthy foods and overeat, but it may also affect where you store fat, according to a review published in Obesity Reports. The authors cite research that suggests chronic psychological stress may cause you to accumulate more belly fat, which is most strongly associated with health issues like heart disease. (13) Employ stress-reduction strategies that make you feel at ease (whether that’s a quick run or a chat with a friend) — use them when you feel anxiety rising.
Be kind to your gut. The gut microbiome, an environment of good and bad bacteria and other microbes in your gut, may also play a role in your risk for metabolic syndrome and obesity, according to an article published in June 2015 in Clinical and Translational Gastroenterology. (14) Eating foods that support healthy gut bacteria, such as pre- and probiotics, can help you maintain a healthy weight, according to an article published in July 2016 in Current Oncology Reports. (15)
Veggies, fruit, whole grains, and legumes are examples of prebiotics, while nonfat or low-fat Greek yogurt, sauerkraut, pickles, and kimchi are examples of probiotics. You’ll also want to be mindful of antibiotics you’re taking because, when not necessary (such as for viral infections, which antibiotics cannot treat), these drugs can throw off the balance of bacteria in your gut, potentially affecting your disease risk, studies suggest.
Get in the right physical state, too. “If you’re not feeling well, you won’t be able to lose weight. Stop worrying about losing weight and start worrying about feeling better,” says Seltzer. That includes taking care of stress and sleeping more. “This will put you in a position where you can be successful.”
Editorial Sources and Fact-Checking
- About Adult BMI. Centers for Disease Control and Prevention. August 29, 2017.
- Etchison W, Bloodgood E, Minton CP, et al. Body Mass Index and Percentage of Body Fat as Indicators for Obesity in an Adolescent Athletic Population. Sports Health. May 2011.
- Overweight and Obesity Statistics. National Institute of Diabetes and Digestive and Kidney Diseases. August 2017.
- Childhood Overweight and Obesity. Centers for Disease Control and Prevention. September 11, 2018.
- Obesity and Cancer. National Cancer Institute. January 17, 2017.
- Hamer M, Batty GD. Association of Body Mass Index and Waist-to-Hip Ratio With Brain Structure. Neurology. February 5, 2019.
- Adult Obesity Causes and Consequences. Centers for Disease Control and Prevention. February 4, 2020.
- Obesity Prevention Source: Environmental Barriers to Activity. Harvard T.H. Chan School of Public Health.
- Weaver JU. Classical Endocrine Diseases Causing Obesity. Frontiers of Hormone Research. January 2008.
- Phelan S, Halfman T, Pinto AM, et al. Behavioral and Psychological Strategies of Long-Term Weight Loss Maintainers in a Widely Available Weight Management Program. Obesity. January 23, 2020.
- Spivey A. Lose Sleep, Gain Weight: Another Piece of the Obesity Puzzle. Environmental Health Perspectives. January 2010.
- National Sleep Foundation Recommends New Sleep Times. National Sleep Foundation. February 2, 2015.
- Scott KA, Melhorn SH, Sakai RR. Effects of Chronic Social Stress on Obesity. Current Obesity Reports. March 2012.
- Parekh P, Balart L, Johnson D. The Influence of the Gut Microbiome on Obesity, Metabolic Syndrome and Gastrointestinal Disease. Clinical and Translational Gastroenterology. June 2015.
- John GK, Mullin GE. The Gut Microbiome and Obesity. Current Oncology Reports. July 2016.