Incidence and Remission of Obesity and Abdominal Obesity with Changes in Physical Activity 

How much of a change in physical activity is needed for patients to benefit, and to reduce rates of obesity and abdominal obesity? 

“Diet and lifestyle changes” are the staple counseling point when talking to patients with newly diagnosed type 2 diabetes. They may be one of the first things that we advise patients to do, but many people have problems changing their diet or lifestyle. Some feel that they’re too busy to change or that change would be too hard. Obesity and abdominal obesity rates are increasing. Physical activity helps with weight maintenance and weight loss. Despite the knowledge that physical activity is essential, we still do not know enough to develop population-based strategies. Few studies have looked at the relationship between changes in physical activity and obesity. Of the studies that have been done, most have had limitations, such as the inclusion of any class of obesity, self-reported weight, and no stratified analyses across obesity groups. Exercise-based studies were often short-term, lasting less than a year, and consisted of small, motivated samples that do not accurately represent the population as a whole.  

This study looked at 113,950 healthy individuals, all of whom were ≥18 years of age. Exclusion criteria included a history of cancer or cardiovascular diseases at the first or second examination, incomplete data at the first examination, having fewer than three observations with valid data on obesity variables, lacking physical activity data at the first or second examination, and a change in obesity status at the second examination. Participants were asked to report how often, for how long, and how intense their physical activities were, either light (i.e. a slow walk), moderate (i.e. a brisk walk), medium-vigorous (i.e. jogging), or high-vigorous (i.e. running). These different intensities were given various metabolic equivalents (3.5 mL/kg/min): Light was given 2.5, moderate was 4.5, medium-vigorous was 6.5, and high-vigorous was 8.5. To calculate the total physical activity per week, the score was multiplied by the frequency and duration. The change in physical activity was the continuous variable and was calculated as the amount of activity at the first and second examinations, divided by the number of years between the examinations. Those with no annual change were categorized as stable, and a change of 3.75 metabolic equivalents per week per year was used to define small to moderate changes, versus moderate to large changes. Obesity was defined as a BMI of ≥25, and severe obesity as ≥30, and a waist circumference of ≥90 cm in men or ≥80 cm in women as abdominal obesity. Additionally, participants were categorized as inactive (0 metabolic equivalent hours per week), insufficiently active (>0-7.49 metabolic equivalent hours per week), or active (≥7.50 metabolic equivalent hours per week). 

Over a mean 5.6-year follow-up, 9,991 (of 83,567) individuals developed overall obesity, while 11,488 (of 91,700) developed abdominal obesity. 3,588 (of 24,153) people with obesity lost enough weight to be classified nonobese, while 3,156 (of 12,688) reduced their waist circumference to nonobese levels. The results showed a nonlinear response between changes in physical activity and incidence and remission of overall and abdominal obesity (P < 0.001 for all). There was a reduction in obesity incidence and an increase in remission among those who increased physical activity, with more significant increases in physical activity showing more favorable results. The authors saw no clear association with obesity outcomes and decreasing physical activity. They did, however, see some tendency towards an increase in obesity remission in those who decreased physical activity. Compared to a stable level of physical activity, a moderate to a substantial increase in physical activity was associated with 14% and 16% lower incidence of overall and abdominal obesity, respectively. A small to a modest increase in physical activity resulted in a 5% decreased risk of obesity, and a 6% decrease in abdominal obesity. Of those with severe obesity, there was a 20% higher remission of abdominal obesity in those with a moderate to a significant reduction in physical activity compared with those with stable physical activity. With an increase in physical activity of 0.01-3.74 metabolic equivalent hours per week, the hazard ratio of overall obesity was 0.95 (95% CI 0.90-1.00). Those that increased their activity by ≥3.75 metabolic equivalent hours per week had a hazard ratio of 0.86 (95% CI 0.80-0.91). 

Surprisingly, a decrease in physical activity was not associated with a risk of obesity when compared to a stable level of physical activity. That said, even small to moderate increases in physical activity resulted in increased obesity remission and a decreased incidence of obesity. These results were from Asian populations, where obesity and severe obesity have different definitions, though the benefits from physical activity are likely to extend to every population.  

Practice Pearl: 

• Even small increases in physical activity result in decreases in obesity, with little to moderate increases in physical activity resulting in a 5% decrease in obesity.  
• Changes in physical activity don’t need to be significant to show benefits.  
• A moderate to significant increase in physical activity resulted in a 14% lower incidence of obesity.  

Martinez‐Gomez, David, et al. “Association of Changes in Physical Activity and Incidence and Remission of Overall and Abdominal Obesity in 113,950 Adults.” Wiley Online Library, John Wiley & Sons, Ltd, 3 Feb. 2020, onlinelibrary.wiley.com/doi/abs/10.1002/oby.22709. 

George McConnell, PharmD. Candidate, LECOM School of Pharmacy 

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