How sugar affects the body and how to avoid energy slumps

Nutrition experts Dawn Menning and Sarah Berry explain how different kinds of sugar act in the body and offer practical tips for avoiding post‑snack energy slumps. "When we taste sugar, the body starts reacting the moment sweetness touches the tongue," says registered dietitian Dawn Menning, noting the brain activates the reward system and releases dopamine.

A 2015 twin study cited in the piece found genetic factors explain about 30% of variance in sweet taste sensitivity, although it is unclear whether that affects how much people eat. Sarah Berry of King’s College London outlines metabolic differences: "Glucose causes the pancreas to release insulin," which helps remove glucose from circulation and store it as glycogen or convert it to fat, while fructose is delivered directly to the liver and can be converted to glycogen or, in excess, to fat.

Both sugars, when eaten in excess, can raise triglyceride levels; fructose is more of a concern for fatty liver and glucose for people who struggle to regulate insulin. Berry also warns that repeated excessive insulin peaks may raise levels of inflammation. The idea of a sugar‑fuelled hyperactive ‘rush’ is not supported by the evidence cited: a 1995 meta‑analysis found sugar did not affect children’s behaviour or cognitive performance, and a 2019 meta‑analysis found no mood‑boosting effects and noted higher fatigue and less alertness within the first hour after ingestion.

Key Topics

Health, Sugar, Glucose, Fructose, Insulin, Triglycerides