The Problem with BMI and the Number You Should Watch

by Erin Palinski-Wade, RD, CDE, LDN
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The Problem with BMI and the Number You Should Watch

Body Mass Index (BMI) had been one of the main criteria used to determine whether a person is overweight or obese. It was developed as a relatively easy screening tool, but it’s far from a perfect measurement. Recently, BMI has drawn criticism as to whether it’s an accurate assessment of health. For example, a high BMI does not take into account muscle mass and other critical factors that may impact health.

“BMI is an indirect measure of body composition meaning that it does not actually measure fat but calculates it based on height and weight,” says sports dietitian Marie Spano, RD, a certified strength and conditioning specialist, adding, “a person with high muscle mass can be categorized as obese or a person with high body fat and a low body weight may have a normal BMI yet an unhealthy amount of fat.”

Recently, many health practitioners are turning to waist-circumference measurements to help predict future disease risk. Waist circumference has been shown to be more reflective of visceral (deep) fat levels and future health risks such as the development of Type 2 diabetes, cardiovascular disease and certain cancers.


Manuel Villacorta, RD, author of the upcoming book “Flat Belly 365” has had personal experience with BMI being inaccurate: “As a short, muscular man, I was once told I was overweight by a nurse based on my BMI.” For himself and his clients, he prefers to use waist circumference to monitor health.


As we learn more about the dangerous role excess levels of visceral fat play in the body, tracking and monitoring changes in waist circumference is becoming more critical to disease prevention. The increased visceral fat coats internal organs like a blanket. Although this fat provides stored energy, it can also secrete inflammatory chemicals called cytokines, which can trigger bodywide inflammation, increasing disease risk.

Although everyone should be aware of their own waist circumference measurement, individuals who have a BMI within the normal range may stand to benefit from tracking this measurement the most. “People who have a normal BMI may carry a good amount of their weight in their stomach which increases their risk for chronic diseases,” says Spano. For men, waist-circumference levels should be below 40 inches, and for women it should be below 35 inches. Even if your waist is within the normal range, you should monitor it for changes over time. A widening waistline may highlight an increased risk for disease.


If you need to reduce your waist circumference, dietary changes are in order: Fill up on produce, whole grains and healthy plant-based fats to help shed visceral fat. “It does not matter how much you exercise, nutrition is 80% of the battle,” explains Villacorta, adding that, “focusing on nutrients and antioxidants that can fight inflammation caused by excess visceral fat and making sure you are eating to promote a healthy gut microbiome may help.”

To eat your way to a slimmer waistline, balance your meals by filling half of your plate with vegetables and fruit. Aim to eat a diet rich in fermented foods such as yogurt, sauerkraut and tempeh to improve gut health and limit eating large amounts of inflammatory foods such as those rich in added sugars.


  • Mark R. Mach

    Fill up on healthy plant-based fats?

    At 4000 kilocalories per pound, there is little reason to fill up on such highly calorically-dense processed foods. (Or any processed foods for that matter.)

    People can eat pretty much as much food as they want under 300 kcal per pound and not gain weight. Furthermore, they can consume relatively large quantities of food that have a calorie density of under 800 kcal/pound can be consumed and still result in weight loss. Anything higher than 800 kcal/pound and you’re risking weight gain.

    So, why would anyone want to fill up on healthy plant-based fats? Isn’t that just going increase the probability that food calorie density is pushed into the danger zone?

    Furthermore, processed fats are pretty much devoid of nutrients and just left with the high calories — something that you should avoid and consume whole foods which have a much higher nutrition to kcal ratio. Sure, there are healthy fats that your body requires, but they are readily available from whole food sources.

    • Spock

      How did you get “processed” out of plant-based fats?

      • Mark R. Mach

        Easy. Fats don’t just appear. They have to be removed from the plant. Nobody said “load up on foods that contain plant-based, healthy fats. It said “fill up on healthy plant-based fats” which implies the fats alone — not as a part of the whole food.

        • Jason

          Avocados, nuts, oilve oils. Not sure why the author stipulates “plant based” Has the vegan myth not been debunked enough yet?

          • Mark R. Mach

            Studies support what you call the “vegan myth.” Plant-based diets, particularly when coupled with whole foods diets, have tremendous health advantages, exhibiting increased longevity, and decreased incidence of many of the modern diseases of affluence. As an added bonus, they are more environmentally friendly, and have ethical advantages as well.

            Sure, avocados and nuts contain fats, but they also have a high calorie density (nuts & seeds are around 1500 – 1700 kcal per pound, and avocado is around 2800 kcal per pound). These are certainly not foods that I would want to “fill up” on. Sure, I eat them, but in moderation (no more than one or two ounces of nuts a day, or a half of an avocado a few times a week).

            Olive oil is just a junk food. Like other processed foods, it has been extracted from the original food (olives), had all fiber, phytonutrients, vitamins, and minerals removed. All that remains is pure FAT with a an extremely high calorie density of around 4000 kcal per pound. Also, studies have shown that while it may be healthier than some other oils, it is certainly not healthy and it would be better to go without. Brachial artery tourniquet tests demonstrate decrease blood flow within hours after consuming olive oil.

            Sure, olive oil may have some essential fatty acids like omega-3s, but it is higher in omega-6, and is a significant source of saturated fat. Besides, people already get too much omega-6 to keep their omega-6 to omega-3 ratio lower, but olive oil itself has an 11:1 ratio which is a bit high.

            If you want olive oil, it is best to keep it in the original form and just eat an olive.

          • Jason

            Thank you for your reply. I don’t think there is any need to fear fat being calorie dense, it’s so much more satiating than other foods that studies show that it becomes self limiting. Some of your comments seem to be almost fat-phobic, personally I don’t fear saturated animal fats as I don’t think my own body would store its excess calories in a form that is harmful to itself. I would suggest looking into the work of eminent cardiologist Dr Aseem Malhotra for more recent science on olive oil.

  • Sam

    I’m not convinced a universal metric like “men should aim for a waist circumference of less than 40 inches” is of much more assistance than BMI to be honest.

    • Jennifer Thompson

      Not unlike BMI, it’s merely a risk categorisation. Those with a metric above certain values have a higher calculated risk of various health ailments (cancers, heart disease, etc). This is why I think 1) BMI is a bit unhelpful with certain body types, but also 2) why freaking out over inaccuracies in BMI assignment is probably unhelpful too.

      Think of it as: people who don’t wear seatbelt suits are more likely to die in a car accident as someone wearing a seatbelt. It doesn’t mean whomever is not wearing a seatbelt will die every time they don’t buckle up.

      • Tam Mailer

        There are as many arguments about seat belts as there are about waist measurements or BMI, but let’s not get into that 🙂

  • Vince

    BMI has always annoyed me. It seems to be good enough measure for some people and absolutely horrible for others. I’ve seen people who naturally have more muscles being consistently told their obese and even morbidly obese, from a young age. That’s awful for self-esteem and for mental health – especially as some people in this category are actually healthy.

  • noncents

    BMI is a garbage stat, but waist circumference isn’t much better. Most with a modicum of intelligence can see people have different sized frames, as much as you can see they are different heights.

    The most accurate gauge is bodyfat and the most efficient way to track it is with calipers you can find for less than $15. The resistance scales are still wildly erratic and thus inaccurate. Once you have taken a 3 or 5 point measurement with help from a friend, a quick pinch on your belly point will give you all the info you need to gauge your progress.

  • Sarah

    So I have been wondering about this a lot. My BMI is 22 (I’m only 120 lb) so well within a healthy range. However my waist circumference is only just under the recommendation for women and I’m not sure why. I follow a very low sugar diet. I eat a mostly plant-based, whole-foods diet and make sure I get healthy gut foods like natural yoghurt and legumes. I do eat a little bit of lean meats like fish, chicken and ham and I eat eggs pretty regularly (don’t know if that is throwing me out). But I have a very small frame so I imagine that for me I should be a fair bit under the “normal” waist circumference because I have a smaller frame than a “normal” person. I don’t understand why I have such a high waist circumference. I had 3 babies in the space of 4 1/2 years, would that have done it? Can someone help me out here?