There is much discussion in the medical literature about which is more important for a long healthy life, being fit or having a healthy weight. There isn’t a simple answer, so I’d like to thank my colleagues for debating these points with me over the past few days.
For sure, FITNESS is VERY important. From a medical standpoint, fitness means being able to perform well on a stress test, indicating ‘all systems go’. Not only do the muscles have the strength and endurance they need to keep you active, but the heart and lung function is good enough to support that activity. Being able to perform well on a stress test is associated with longer life.
On the other hand, the impact of WEIGHT on longevity is more of a grey issue. In medicine, references to weight are usually expressed as the BMI, which is calculated as the weight in kilograms divided by (the height in meters) squared – i.e., weight in relationship to height.
Here’s a link to a site with a BMI calculator, with more information about the limitations of that measurement. A BMI of 18.5-25 is considered ‘normal’, 25-30 ‘overweight’, while 30-35, 35-40 and >40 are different levels of ‘obese’. As an example, given a height of 5’3”, a weight of 115 calculates out to a BMI of 20, 140 pounds gets you to a BMI of 25, and 170 pounds on the same 5’3” frame gets to a BMI of 30.
Some prior studies have referred to the ‘obesity paradox’. Whereas obesity is usually associated with worse survival, in these studies a higher BMI seemed to be associated with better survival from cardiovascular disease. This highlights a major problem with using BMI – it doesn’t account for build (narrow vs broad frame) and it doesn’t look at where the weight is concentrated (large muscles vs fat in the belly vs fat in the thighs). Looking at the BMI alone can give you a false impression of a person’s health status.
For instance, someone with ‘normal’ weight as determined by BMI can have a narrow frame and a protuberant abdomen. Abdominal or CENTRAL OBESITY is much more highly associated with high blood pressure, high cholesterol, and type two diabetes. Someone with lots of weight in their belly has a higher likelihood of illness than someone with fat distributed in their thighs or with bulky muscle anywhere, even though their BMIs might all be the same. Looking at these variations, some studies (Padwal and Sahakyan referenced below) have shown that increased waist circumference is associated with increased mortality. A ‘high’ waist circumference is generally defined as over 35” in women and over 40” in men. Other studies have shown that this higher risk associated with obesity can be counteracted, at least to some degree, by a better level of fitness.
Obesity (BMI > 30) has increased dramatically from 1960 through 2000, but death rates haven’t increased as much. Why not? Likely due to more aggressive and effective management of blood pressure, cholesterol and diabetes. Does that make the high BMIs OK? Not at all – the FINANCIAL COST of obesity-related illnesses is tremendous and the DISABILITY associated with the increased weight, especially in the older population is very significant. And, in fact, that disability has increased over time, relative to normal-weight adults.
With effective medication, people may not die as prematurely from their weight-related illnesses as they would have in the past, but in general, they don’t get around as easily as their normal-weight counterparts. I am concerned that when medications lower the BP, cholesterol and sugar, people are less motivated to exercise to achieve control of those parameters. Regular exercise, leading to improved fitness, is really the ticket to a longer, more active life. It should be considered as part of the prescription. Take your statin, your blood pressure and diabetes medications, AND exercise 30 minutes most days. ALL of these aspects are important for overall wellbeing.
Even for those in the ‘normal weight’ category by BMI (~ 20-25), fitness counts. Being normal weight and ’unfit’ is associated with twice the mortality of a normal-weight fit adult. ALL of us who are able to do so should be encouraged to exercise at least 30 minutes most days of the week. It’s remarkable how many good effects exercise has been associated with – avoiding diabetes, treating high BP, improving cholesterol ratios, decreasing the rate of dementia and improving one’s sense of well-being, just to name a few. And these can be achieved with exercise even without weight loss. It’s the least expensive medication around!
In September, 2016, an article in the American Journal of Medicine showed that the rate of death was lower in those more fit (able to exercise to 10 METS on a stress test) compared to those who were not able to achieve 6 METS, in all BMI categories. One MET is the energy expended at rest. Casual walking or biking would be in the 3-5 MET range. Jogging or more vigorous aerobic activity might be 8 METS and above. When you do a stress test in a doctor’s office, each ‘stage’ in which the speed or the incline is increased represents an increase in the number of METS. If you’ve already had a stress test, you can ask how many METS you achieved before you had to stop.
Obesity has surpassed smoking as the #1 cause of PREVENTABLE disease and disability. If you’re in a position to alter your body composition or exercise status, NOW is the time to start. No matter your age, if you would like to be active ten years from now, your best chance at acheiving that is to be moving NOW. Fitness level counts in everyone whether normal weight or obese. Don’t get stuck on how many pounds you should lose, or what your waist circumference is, just check with your doctor, and if it’s OK, keep moving. Aim for a higher fitness level by gradually increasing the duration and/or intensity, as approved by your personal physician. Think of it as a marathon, not a sprint. Slow and steady without injuries wins the race! Get ready, get set …….
McAuley, et al. AJM 129(9): 960 – 965. Sept 2016.
Padwal R, Leslie WD, Lix LM, Majumdar SR. Relationship Among Body Fat Percentage, Body Mass Index, and All-Cause Mortality: A Cohort Study. Ann Intern Med 2016; 164:532.
Sahakyan KR, et al, Normal weight central obesity: implications for total and cardiovascular mortality. Ann Intern Med. 2015; 163(11): 827-835.
Info about METS: https://en.wikipedia.org/wiki/Metabolic_equivalent