Reduced Fat Oxidation as a Potential Pathway Linking Early-Life Adversity to Obesity Risk: Evidence From Vanuatu

Adverse environmental conditions during early life can increase the risk of obesity in adulthood, but the underlying mechanisms are not completely understood. Here, we test the hypothesis that early-life adversity leads to a lower metabolic rate and reduced fat oxidation, factors expected to increase fat accumulation.

We used data collected from 80 children and adolescents (aged 6-15 years; n = 39 females) living in Vanuatu. Relative lower limb length, calculated as the ratio of lower limb length to stature, was used as a surrogate measure of each individual's early-life environmental conditions, with a shorter relative lower limb length considered indicative of greater adversity. Fasting resting metabolic rate (RMR) and respiratory quotient (RQ) were measured with indirect calorimetry, and a higher RQ value was considered indicative of a lower rate of fat oxidation.

We found that, in a linear mixed-effects model including age, sex, and fat-free body mass as fixed effects and community and family as random effects, relative lower limb length was not significantly associated with RMR (p = 0.95). However, in a separate model, relative lower limb length was significantly negatively associated with RQ (p = 0.036), after accounting for the same fixed and random effects.

The latter finding suggests that adverse environmental conditions during early life may lead to reduced fat oxidation, which has the potential to increase the risk of obesity later in life. This finding might partially explain the so-called double burden of malnutrition (the co-occurrence of undernutrition and obesity) currently affecting many low- and middle-income countries.