Fructose intervention for 12 weeks does not impair glycemic control for incretin hormone responses during oral glucose or mixed meal tests in obese men

A study entitled “Fructose intervention for 12 weeks does not impair glycemic control for incretin hormone responses during oral glucose or mixed meal tests in obese men” by Matikainen et al. was recently published in Nutrition, Metabolism & Cardiovascular Diseases. The purpose of the study was to determine if habitual fructose consumption (75g/d for 12 weeks) resulted in incretin mediated worsening of glycemic control.

Researchers recruited “healthy obese men” based on the following criteria: waist circumference ˃ 96cm, body mass index (BMI) between 27 and 40 kg/m2, stable weight for the last 3 months, low-density lipoprotein cholesterol (LDL-C) < 4.5 mmol/l and triglycerides (TG) < 5.5 mmol/l. None of the subjects reported taking any medications or hormones known to mediate glucose of lipoprotein metabolism. A total of 65 participants completed the study with full data sets.

Each subject consumed their normal diet supplemented with 75g of fructose daily for 12 weeks. Fructose was provided in lemon flavored carbonated beverages prepared as 7.6% (w/w). Participants received three, 330ml bottles per day equaling 303 kcals from the fructose sweetened beverages. They were instructed to consume their beverages together with their three main meals while maintaining their normal ad libitum diets and physical activity routines. Each participant kept a 3-day food record before the intervention and then again within 2 weeks of the conclusion of the intervention.

Prior to the start of the fructose intervention, subjects participated in 3 study visits: 1) oral glucose tolerance test (OGTT), 2) mixed meal test, 3) magnetic resonance imaging. During the mixed meal test, participants were asked to consume a meal (63g Carbohydrate, 56g Fat, 40g Protein, 927kcals) followed by a series of blood draws. Magnetic resonance spectroscopy was used to measure liver fat content.

Researchers note the following results:

  • On average, participants were 48 years old and had a BMI of 30.6 kg/m2 (obese)
  • Before the intervention, there were no correlations between fasting GLP-1 or GIP with BMI, liver fat, subcutaneous fat, visceral fat, fasting glucose, or fasting insulin.
  • Fasting GLP-1 was correlated with HOMA-IR prior to intervention.
  • During the OGTT – glucose, insulin, GLP-1 and GIP responses were similar before and after the fructose intervention.
  • Fasting HOMA-IR, insulinogenic index, and disposition index did not change significantly during the fructose intervention.
  • Fasting and postprandial PYY concentrations were not affected by fructose intervention.
  • Fructose intervention did increase fasting TG slightly by significantly (mean: 1.56 (before) 1.66 (after) p-value 0.032).
  • Post prandial TG was also higher after fructose intervention.
  • GLP-1 and GIP did not differ before or after fructose intervention during the mixed meal test.
  • The fructose intervention resulted in an increased energy intake but this was not statistically significant.
  • The 12 week fructose intervention resulted in a slight but significant increase in weight from 99.2kg to 100kg.
  • Liver fat increased 9.2% but subcutaneous and visceral fat did not change.
  • After dividing data up by weight stable, weight gain, and weight loss groups and conducting statistical analysis, researchers found that the result remained the same.
  • After dividing data up by liver fat responses, they found that the liver fat increase group had higher TG, fasting insulin, and HOMA-IR.

Researchers conclude “that 75 g daily fructose from SSBs for 12 weeks does not impair gut incretin response or glucose tolerance in obese males, even in the presence of moderate weight- or liver fat gain.”