Body weight is relative. This is something that I’ve said for years: Being overweight at age 12 or 20, with continued weight gain is not the same health risk as being at within healthy weight range and then gaining weight in your 50s.
A new study published in the Journal of the American Geriatric Society suggests that older adults classified as overweight may have a lower mortality risk.
With so much marketing for GLP-1 medications for weight loss these days, it’s important to understand how weight is evaluated through the life cycle. How is overweight or obesity evaluated and what are the risks from a clinical standpoint? In clinical dietetics and medicine, we typically use two measures to evaluate weight status – body mass index (BMI) and waist circumference. However we also evaluate lifestyle, medical history, family and social history in our assessments.
What Does Healthy Body Weight Look Like in Older Adults?
The study examined associations of body mass index (BMI) category and waist circumference (WC) independently over a 14-year period, on all-cause mortality risk among US adults aged 65 or over.
The study found that “Compared with normal BMI (18.5 to 24.9), being classified as overweight (BMI 25 to 29.9) was associated with substantially lower mortality risk in both males and females”. In males, even a BMI indicating obesity at 30.0 to 34.9 (class I) or 35-29.9 (class II obesity) was associated with lower mortality risk.
However, waist circumference told another story. Men with a waist measuring over 40 inches and women with a waist over 35 inches had a 24% higher risk of early death, regardless of BMI. Health risk is increased with a waist circumference above 31.5 inches for women. For men, risk increases when waist measures above 37 inches. To take your waist measurement, loosely wrap a tape measure above hip bone, in line with belly button.
Being classified as underweight was associated with higher mortality risk in both sexes. Men or women who were underweight were associated with substantially elevated health risk whether with a low waist or a high waist circumference. The study points out that the redistribution of fat tissue toward the belly region may further modify health risks (and impact waist circumference) in older women. Men might see a difference due to the natural loss of testosterone with age, but it’s not as apparent or influential on waist measurements.
BMI Limitations
When evaluating health, BMI is only one data point. It assesses for weight and height, but it does not account for body composition. Your body composition includes both fat mass and fat-free mass (bones, organs, muscles, and water). BMI also does not offer a complete picture of health nor disease risk. Someone who lifts weights regularly and is more muscular generally have a high BMI. That number may not correlate to the risk factors associated with obesity.
BMI also does not encompass other important factors that relate to health. Factors like diet quality, dietary patterns and habits, and physical fitness also matter. Someone may be in the “normal” range category and be unhealthy. Or the “obese” category and be healthy and without other risk factors or disease. And as this study showed, for older adults, waist measurement carries more weight than BMI.
Flat Stomachs aren’t Medicine
You can hardly scroll through your news feed or social media these days without seeing or hearing something about “belly fat”. Sometimes these statements are positioned in a way to make you believe this is a new phenomenon. Midlife “spare tires” aren’t new.
Of course waist circumference measurements are related to fat accumulation around the mid-section. Checking your waist measurement can be meaningful, but having a “flat stomach” or washboard abs isn’t necessary to reduce your health risk. Having fat around the belly is normal, especially for those over age 55. On the other hand, having a flat stomach is not a health indicator.
Body fat is part of normal body composition. Clinically, it’s expressed as a percentage of total body weight. It can be professionally estimated in a variety of ways (body fat calipers, bioelectrical impedance scales, hydrostatic weighing).
Healthy body fat varies by sex and age too.
Changes in hormones in various life stages impacts body fat. For young women ages 12 to 20, a healthy body fat percentage may range anywhere from 20-27% of their body weight. For women over age 20, 25 to 31% is typical. Healthy body fat in older women is defined as less than 36%. However, according to the CDC, the average is around 40% body fat. A healthy body fat range for men is 18-24%. Body fat levels are often lower in athletes. To maintain healthy menstruation, women are cautioned not to drop below 20%.
It’s understandable that the public would think that their belly bulge is due to the increasing prevalence of obesity in the United States. The obesity rates have been climbing since the 1980s. Current data shows that 40 percent of the current US population classified as such. If you study art, it appears that, for centuries, humans developed extra fat around the waist and abdomen at mid-life. People also have different body structure. Due to genetic factors, they may have different bone structure and body composition. It’s normal for bodies to change with age. And it’s quite typical for many post-menopausal women to accumulate fat in their mid-section when estrogen levels drop.
Weight is only one number
The recent study evaluating BMI in older adults and what we know about body composition through life tells us a few things. Focusing only on how much you weigh or your BMI does not paint a complete picture of your health risks. In addition, body fat composition is different between the sexes, and it is normal for it to change as we age through life. Health risk assessment should include estimating body fat. For instance, two people can be the same weight and height, but their body composition can be very different. One may have little muscle, and more fat deposited throughout the body. While the other has less body fat, and more muscle at the same weight. This is just one reason why the scale weight is not always of value.
While you may want to lose weight, there are other measurements to consider. Fitness level, healthy bloodwork, waist circumference, and muscle mass, are also important to check and keep tabs on. Becoming obsessed with a number on the scale can also take a psychological toll and impact your self-worth. Try not to compare your 55-year-old weight with your 35-year-old weight. It’s unrealistic, and may not have any bearing on your health risks.
Instead, focus on staying strong or getting stronger by incorporating regular resistance training into your fitness routine. Check your waist measurement. Add more gentle movement each day. Eat a balanced diet of foods that you enjoy. That is a winning combo for healthy aging. Give yourself grace and understand that body changes are a normal part of living, and aging.
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