An article published online on September 14, 2015 in the peer-reviewed journal Obesity Research & Clinical Practice presented an analysis of dietary data from 36,377 U.S. adults, collected in 1971-2008 within the National Health and Nutrition Survey (NHANES).

Ruth Brown and colleagues from the School of Kinesiology and Health Science, York University, Ontario, Canada found a 10-14% increase in body mass index (BMI), total caloric intake, and carbohydrate intake between 1971-2208, along with a 5-9% decrease in fat and protein intake. In a comparable time period (1988-2006), frequency of physical activity in leisure time increased 47-120%. Surprisingly, the authors found that the BMI predicted using a mutually adjusted model for a given amount of caloric intake, macronutrient intake, or physical activity, was up to 2.3 kg/m2 higher in 2006 compared to 1988.

Based on their findings, the authors suggested that “other factors beyond total caloric intake [and physical activity] may be contributing to the epidemic rise in obesity.” Chemical exposure could be one of these factors. The authors pointed out that chemicals may have contributed to altering the relationship between diet, energy intake, and weight gain over time, for example by affecting the composition and functioning of gut microbiota.


Brown, R., et al. (2016). ”Secular differences in the association between caloric intake, macronutrient intake, and physical activity with obesity.Obesity Research & Clinical Practice 10(3):243-255.