Overweight? Overeating– not our modern, sedentary lifestyle– is the likely culprit

You hear the irony on the news – we see famine in parts of our planet yet a global obesity epidemic has worsened over the past 20 years.  It’s particularly obvious in the U.S.: more than 1/3 of U.S. adults (35.7%) and approximately 17% (or 12.5 million) of children between 2—19 years old are obese.

What does it mean to be “obese”?  The Center for Disease Control (CDC) defines an obese person as one with a body mass index (BMI) of 30 or higher, while an overweight person has a BMI of 25 or higher.  Go ahead and check your BMI with an online table or calculator and report back.

More than just an image issue

The situation is urgent for many people:  as your weight increases to reach the levels referred to as "overweight" and "obese," you face higher risks for a number of real and problematic health issues:

• Coronary heart disease
• Type 2 diabetes
• Hypertension (high blood pressure)>
• High cholesterol / high levels of triglycerides
• Stroke
• Cancers (endometrial, breast, and colon)
• Liver and gallbladder disease
• Sleep apnea and respiratory problems
• Osteoarthritis (a degeneration of joint tissue).

These conditions – and, thus, overweight and obesity – are linked to larger-scale suffering as well, not to mention increased medical costs ($1,400 higher in 2008 than a normal weight person) and higher indirect costs (i.e. income lost from decreased productivity or absenteeism from work).   Studies have found that obesity increases lifetime medical care costs for these diseases by 50% above a healthy-weight baseline.  So maintaining a healthy weight is good for your wallet, as well as your well-being. 

Environmental and genetic factors contribute to body type and condition, but our behavior (aka diet and exercise) is the key aspect of our lives that we can change to prevent and help treat weight-related illness.  But which behaviors are most likely to prevent weight gain?

Energy savers 

According to the CDC and the World Health Organization, overweight and obesity result from eating too many calories and not getting enough physical activity. As more of us remain seated at our computers or on motorized transportation, we do get much less physical activity than our ancestors did.

However, it seems that overeating, more than our lack of activity, is to blame for gaining weight, according to recent research led by Herman Pontzer of Hunter College. 

Pontzer and his team measured the energy (calories) burned by members of the Hadza people, a group of traditional hunter-gatherers in Tanzania that lead physically active lives.  The Hadza walk miles each day: women forage for tubers, berries, and wild plants while carrying water or babies on their backs, and men collect honey and hunt with bows & arrows. 

Hadza men returning from a hunt. Photo: Andreas Lederer

The Hadza don’t suffer from Western diet-related diseases such as heart disease or diabetes, a testament to their active lifestyle.  However, despite their greater physical activity, the number of calories that the Hadza burned per day was no different from that of typical adults in Europe and the U.S.  

How could this be?  I wondered this too.

Apparently, even for very active people, the body’s continual internal maintenance of its temperature, cells and systems – not our daily run, swim, or Zumba class – accounts for most of the calories burned in a given day.  

Pontzer and his colleagues think that energy (calories again) used by the Hadza for normal at-rest functioning may be less than that of less active people, so their total energy expenditure was similar to those among modern populations.  In other words, our bodies may be able to adjust our energy needs to our daily routines to keep total energy expenditure stable. 

I’m a huge fan of exercise, and I believe it is essential to staying fit, both physically and mentally (yes, I go crazy after a couple of days if I cannot exercise, though this may stem from the equally great joy I get from eating!).  But despite the numerous health benefits of working out, there seems to be little correlation between a person’s level of physical activity and how fat he or she becomes.  Or, in Pontzer’s words, “We’re getting fat because we eat too much, not because we’re sedentary.”