Cheryl Roumen

Lifestyle interventions are reported to reduce the risk of type 2 diabetes in high-risk individuals after mid- and long-term follow-up. Information on determinants of intervention outcome and adherence and the mechanisms underlying diabetes progression are valuable for a more targeted implementation. Weight loss seems a major determinant of diabetes risk reduction, whereas physical activity and dietary composition may contribute independently. Body composition and genetic variation may also affect the response to intervention. Lifestyle interventions are cost-effective and should be optimized to increase adherence and compliance, especially for individuals in the high-risk group with a low socioeconomic status, so that public health policy can introduce targeted implementation programs nationwide. The aims of this review are to summarize the mid- and long-term effects of lifestyle interventions on impaired glucose tolerance and type 2 diabetes mellitus and to provide determinants of intervention outcome and adherence, which can be used for future implementation of lifestyle interventions.

Aims  To determine the effect of a lifestyle intervention on serum transferrin and ferritin levels and the relationship between changes in transferrin and ferritin and changes in glucose tolerance and insulin resistance.Methods  Randomized controlled lifestyle intervention directed at a healthy diet and increased physical activity in subjects with impaired glucose tolerance.Results  After 1 year, the change in ferritin levels in the intervention group as compared with the control group did not reach statistical significance (P = 0.06). Transferrin change was independently related to the change in homeostasis model assessment of insulin resistance and ferritin change was related to the change in 2‐h free fatty acids.Conclusions  Changes in insulin sensitivity and postprandial lipid metabolism are related to changes in iron metabolism.

Objective  To determine the effect of a 3‐year diet and exercise lifestyle intervention, based on general public health recommendations, on glucose tolerance, insulin resistance and metabolic cardiovascular risk factors in Dutch subjects with impaired glucose tolerance (IGT).Methods  The study was a randomized controlled lifestyle intervention over 3 years. A total of 147 IGT subjects (75 male, 72 female) were randomized to the intervention (INT) group or control (CON) group; 106 subjects (52 INT, 54 CON) completed 3 years of intervention. Annually, glucose, insulin and free fatty acid (FFA) concentrations were determined fasting and after an oral glucose tolerance test. Measurements of body weight, serum lipids, blood pressure and maximal aerobic capacity were also performed.Results  Analysis of those who completed the 3‐year trial, showed that the lifestyle intervention improved body weight (INT −1.08 ± 4.30 kg; CON +0.16 ± 4.91 kg, P = 0.01), homeostatis model assessment index for insulin resistance and 2‐h FFA. Two‐hour glucose concentrations improved in the INT group, the difference being most pronounced after 1 year, with a return to baseline values after 3 years, from 8.59 ± 1.55 to 8.55 ± 0.34 mm; in contrast, 2‐h glucose deteriorated in the CON group—from 8.46 ± 1.84 to 9.35 ± 2.50 mm (P = 0.02). In the INT group, diabetes incidence was reduced by 58% (P = 0.025).Conclusion  Our lifestyle intervention showed a sustained beneficial effect on 2‐h glucose concentrations, insulin resistance and 2‐h FFA, even after 3 years. Our lifestyle intervention is effective, but for implementation more information is needed about factors influencing adherence.