by Barbara Berkeley, MD
The patient in front of me is Mr. C, a 308-pound man who has been sent by one of my favorite referring doctors. This doctor truly cares about the health of his patients and it shows. In fact, Mr. C’s physician is a triathlete, eats for health and practices what he preaches. He’s never been overweight. His clients are devoted to him and Mr. C is no exception. But Mr. C. is worried. He genuinely wants to lose weight but the doctor he so much wants to please has told him that he needs to reach 170 pounds: the white or “healthy” zone of the BMI chart. “Doc,” he says earnestly. “Is that possible? I’ve never been that light, not even in high school.”
Twenty years ago,the term BMI was part of the foreign language of doctors, a measurement that was recorded on the chart and remained obscure to patients. Today, nearly every dieter understands, (and sometimes obsesses about), his or her niche on the BMI chart.
BMI, or Body Mass Index, is a shorthand that describes the relationship between your body height and weight. The measurement first saw the light of day in the mid 1800s, invented by a scientist named Adolphe Quetelet. In order to compare peoples' masses, Quetelet proposed a method which divided weight by height squared. Current BMI figures are still based on the same equation: weight in kilograms/ height in meters squared. Today, high BMIs denote overweight and obesity. The cut-offs are as follows: BMI of 25 or less = normal, BMI of 25 to 30 = overweight, BMI of 30 to 35 = obese, BMI of 35 or greater = morbid obesity. On many BMI charts, the obese weights are colored red, the overweight weights yellow and the normal weights white. (You can find a typical BMI chart on my practice's website: www.weightmp.com).
Because BMI looks at weight without distinguishing whether it is coming from fat, bone, or muscle, people with denser bone structure or those with large muscles masses can have high BMIs. I am frequently asked by patients whether a weight that increases or fails to drop might be coming from a new muscle-building gym regimen. Alas, the answer is generally no. Unless you are built like Dwight Howard or Arnold Schwarzenneger, the amount of muscle you gain in the average gym is not causing your BMI to rise. This is especially true for women, who can get great toning and definition from lifting, but are generally not capable of building large amounts of new muscle mass.
In my book, Refuse to Regain, I reference the work of Dr. Walter Willett of Harvard School of Public Health. Dr. Willett has been in charge of the comprehensive Nurse’s Health Study for some years, a study which shows that the risk of diabetes, hypertension, gallbladder and coronary artery disease starts to rise at BMIs that are far below the 25 we consider “just overweight.” Dr. Willett has said that this data was known, but ignored when committees set the “normal” cutoff for BMI. He believes that the reason is simple. If normal BMI were lowered to somewhere around 22, the vast majority of America would be classified as overweight.
While Dr. Willett is one my dietary and medical heroes, I have a somewhat different take on BMI. Yes, we know that weight gain impacts our health negatively. We know that even small amounts of weight gain put us at risk. But what happens once the horse is out of the barn? Once we have gained that weight, incurred that new risk, what then? Are the rules for “healthy” BMI the same after gain has occurred? This question brings us to a larger and more fascinating issue: Is there some permanent change that occurs within us once we have been overweight that changes those rules?I believe the answer is yes.
What I call POWs (previously overweight people) seem to be quite different from NOWs (never overweight people). As someone who was a NOW in my earlier years and is now a POW, I can attest to the fact that my physiology has changed. Can I prove this scientifically? No. We have now crossed over into the area of observation and opinion. Read on with that knowledge.
In my view, weight gain occurs when the normal mechanism that controls and stabilizes weight is damaged by over-exposure to elements of the SAD (standard American diet). Once the damage is done, I believe that we remain prone to weight gain. We can prevent this by avoiding the foods that caused the damage in the first place, but we must be extra careful. Most POWs cannot eat mindlessly anymore.
This tendency to weight regain may also have to do with fat cells which remain in the body, but which no longer contain fat. No one knows if depleted, empty cells signal the brain or cause other kinds of hormonal havoc. So what does this have to do with optimal BMI? When we gain weight, the body has to manufacture new fat cells to store the oily triglycerides which are being created. These cells are supported by a scaffolding of connective tissue and muscle. After weight loss, the fat cells are emptied, but some of the tissue may remain. Many POWs find that they simply cannot lose enough weight to reach the white area of the BMI chart. This may well be because the BMI chart is based on the weights of those who have never been heavy, in other words, the weights of NOWs. Since they have never manufactured new fatty tissue, their baseline weights are lower.
I love what I do, but I have written before about the one part of my job I don’t enjoy. That would be the very last phase of a patient’s weight loss. Almost without exception, my patients are unhappy with their final weights. This happens even when they have lost 60, 80, or 150 pounds. Each one longs to to get down “just a little more!” Each one feels like a failure for not reaching the white zone. This is the point at which BMI charts become tyrannical, and for no good reason. The rules for optimal BMI in the POW are different, just as pretty much everything else is different for POWs. Since there are no established guidelines for optimal weight in the POW, I can only offer my own take.
1. If you have been significantly overweight, a loss of 20% of your pounds is highly successful and is what I usually target. If you’ve lost more, great!!
2. Your optimal BMI should be the one at which you have eliminated or greatly minimized any weight related medical issues (especially blood pressure, diabetes, and lipids). In some people, remnants of the problem will remain, but the vast majority can expect significant improvement and decrease of medications.
3. Your optimal BMI should be one at which you can comfortably maintain.
Number three is probably the most important guideline, because weight loss is of no consequence if it ends in regain. POWs who push themselves to very low weights often do so at the expense of muscle tissue. If you start to look wasted, your vital muscle mass may be dissipating. At such low weights, and without muscle to help out with calorie burning, you will have to make do with what I call “two peas and a bean”. That’s not fun, that’s not life, and that’s not sustainable.
Are BMI charts important at all? Yes. They remain vital for judging the weights of NOWs, like our kids, young adults and that minority who remains at normal weight. If we can prevent them from converting to weight gainers, they will not have to deal with the permanent changes that dog the rest of us. As parents, educators, doctors and public citizens, this is a worthwhile goal and one that our health care system should be targeting. But for the rest of us? Shoot for maintenance, comfort, health, mobility. These will stand you in good stead whatever your zone or color.
