Sweetened drinks cause muscles to prefer burning sugar to fat
In a fascinating study just published in the European Journal of Nutrition, the authors demonstrate that just four weeks' consumption of sugar-sweetened beverages causes gene activity in muscles to shift from burning fat to sugar. The authors observe:
"Chronic sugar-sweetened beverage (SSB) consumption is associated with obesity and type 2 diabetes mellitus (T2DM). Hyperglycaemia contributes to metabolic alterations observed in T2DM, such as reduced oxidative capacity and elevated glycolytic and lipogenic enzyme expressions in skeletal muscle tissue. We aimed to investigate the metabolic alterations induced by SSB supplementation in healthy individuals and to compare these with the effects of chronic hyperglycaemia on primary muscle cell cultures."
In other words, it's well known that chronic elevations in blood sugar (as in type 2 diabetes) increase muscle enzymes that break down sugar (glycolytic) and build up fat (lipogenic). They wanted to investigate the effect of SSBs on healthy individuals and the extent to which their muscles would shift from burning sugar to burning fat. In their study healthy, lean subjects were given sugar sweetened beverages for four weeks (about 140 grams of glucose per day). Body composition, respiratory exchange ratio (RER), insulin sensitivity, muscle metabolic gene and protein expression were assessed before and after. The data showed a reduced ability to burn fat:
"SSB supplementation increased fat mass (+1.0 kg), fasting RER, fasting glucose (+0.3 mmol/L) and muscle GAPDH mRNA expressions. PGC1α mRNA was reduced. Trends were found for insulin resistance, and MondoA protein levels. Primary myotubes showed elevations in GAPDH, ACC, MondoA and TXNIP protein expressions."
In other words, muscles metabolism became less efficient and underwent a persistent shift to preferentially burning sugar and storing fat. This is the unhealthy adaptive change that occurs in the obese and diabetic. The authors conclude:
"Four weeks of SSB supplementation in healthy individuals shifted substrate metabolism towards carbohydrates, increasing glycolytic and lipogenic gene expression and reducing mitochondrial markers."
Food and drink are indeed 'genetic response modifiers'.