No Additional Benefits on Cardiometabolic Risk Parameters of Reduced Red Meat or Increased Fiber Intake in an Energy-restricted Diet
By Heather Nelson Cortes, PhD and Kevin C Maki, PhD
To date, results from epidemiological studies have suggested that a high intake of red meat is associated with a higher risk of developing type 2 diabetes (T2D) while high fiber intake is associated with a lower risk 1-5. Furthermore, high intakes of red meat have also been suggested to be linked to increased risks of cardiovascular disease (CVD) and mortality 6,7. One of the main approaches for reducing risk of T2D and CVD is weight loss 8-10. Research findings have also suggested that cardiometabolic risk can be improved with dietary modification independent of weight loss 11,12.
Willman et al. completed a 6-month, randomized controlled dietary intervention trial to assess whether lower intake of meat or higher intake of dietary fiber would have additional benefits when incorporated into an energy-restricted diet 13. Subjects were randomized to one of three groups with all groups being instructed to reduce their caloric intakes by 400 kcal/d below their weight-maintenance requirements and exercise 3 hours/week. The control group just decreased their caloric intake. The “no red meat” group avoided red meat, but was able to eat turkey, fish or chicken, and subjects in the “fiber” group increased their fiber intake to at least 40 g/day. The researchers also analyzed 9-month follow-up data from the Tuebingen Lifestyle Intervention Program (TULIP) cohort, which included subjects (n = 229) at increased risk of diabetes 14. The intervention in TULIP consisted of increased physical activity and decreased caloric intake.
All participants in the 6-month trial lost weight (mean 3.3 ± 0.5 kg, P < 0.0001). Glucose tolerance and insulin sensitivity improved (P < 0.001), and body and visceral fat mass decreased in all groups (P < 0.001), with no difference among the groups. Similarly, liver fat content decreased (P < 0.001) with no differences among the groups. The liver fat decrease correlated with the decrease in ferritin during intervention (r2 = 0.08, P = 0.0021). This association between ferritin and liver fat changes was confirmed in TULIP (P = 0.0084).
Comment. Neither the absence of dietary red meat nor the increase in fiber intake had an additional effect beyond calorie restriction and exercise on risk markers for T2D or CVD. These results confirm that weight loss can lead to improvement in glucose metabolism, body fat composition and liver fat content and do not indicate incremental benefits for restriction of red meat intake or increasing dietary fiber intake. Additional research is needed to assess effects of these dietary factors during weight loss maintenance.
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