According to research published in the obesity issue of AACC journal Clinical Chemistry, people are at greater risk of obesity if they produce higher than normal levels of insulin after eating processed carbohydrates.
Researchers led by Harvard Medical School’s Dr David Ludwig have completed the first Mendelian randomization (a type of genetic analysis) to determine whether carbohydrate-induced insulin production leads to weight gain.
The researchers studied data from more than 26,000 individuals to identify genetic variants linked with high insulin levels 30 minutes after glucose administration (insulin-30). Statistical analysis of data from about 140,000 additional people revealed that these genetic variants were “strongly associated” with higher body-mass index.
For example, based on the researchers' findings, a 5'2" to 5'9" person with insulin-30 one standard deviation (SD) below average would weigh 5.5-6.8 pounds less than the same person with above average insulin-30 (+1 SD).
The researchers concluded that this suggests a genetic predisposition to high insulin after carbohydrate consumption causes increased weight gain.
"It appears that a lifetime of high glucose-stimulated insulin secretion … is obesogenic," said Dr Ludwig. "These findings lend additional support to the carbohydrate-insulin model of weight regulation, which postulates that diets high in glycemic load promote weight gain through the anabolic effects of increased insulin secretion."
Controversy surrounding the carbohydrate-insulin hypothesis
Low carb diets have gained popularity among consumers who believe they will help in weight management.
This approach is supported by the carbohydrate-insulin hypothesis, which stipulates that eating fast-digesting carbohydrates (such as refined grains, potato products and sugars) is linked to weight gain.
The insulin theory posits that higher carbohydrate diets increase insulin secretion, which then drives fat storage and essentially 'starves' muscles and organs of energy. Low carb diets are thought to be effective because lowered levels of insulin allow the body to begin metabolising fat and increase energy expenditure.
However, there is still a significant amount of controversy around this hypothesis. One recent study, published in journal Cell, found that the energy expenditure of people on a low carb diet actually reduced. Using two control groups, the researchers noted that those on the reduced carbohydrate diet experienced “significantly lower” 24-hour energy expenditure and sleeping energy expenditure.
Source: Clinical Chemistry
Published online ahead of print: DOI: 10.1373/clinchem.2017.280727
“Genetic Evidence That Carbohydrate-Stimulated Insulin Secretion Leads to Obesity”
Authors: Christina M. Astley, Jennifer N. Todd, Rany M. Salem, Sailaja Vedantam, Cara B. Ebbeling, Paul L. Huang, David S. Ludwig, Joel N. Hirschhorn, Jose C. Florez