Limited evidence for effects of diet for type 2 diabetes from systematic reviews

Lifestyle counseling in routine care and long-term glucose, blood pressure, and cholesterol control in patients with diabetes

OBJECTIVE

In clinical trials, diet, exercise, and weight counseling led to short-term improvements in blood glucose, blood pressure, and cholesterol levels in patients with diabetes. However, little is known about the long-term effects of lifestyle counseling on patients with diabetes in routine clinical settings.

RESEARCH DESIGN AND METHODS

This retrospective cohort study of 30,897 patients with diabetes aimed to determine whether lifestyle counseling is associated with time to A1C, blood pressure, and LDL cholesterol control in patients with diabetes. Patients were included if they had at least 2 years of follow-up with primary care practices affiliated with two teaching hospitals in eastern Massachusetts between 1 January 2000 and 1 January 2010.

RESULTS

Comparing patients with face-to-face counseling rates of once or more per month versus less than once per 6 months, median time to A1C <7.0% was 3.5 versus 22.7 months, time to blood pressure <130/85 mmHg was 3.7 weeks versus 5.6 months, and time to LDL cholesterol <100 mg/dL was 3.5 versus 24.7 months, respectively (P < 0.0001 for all). In multivariable analysis, one additional monthly face-to-face lifestyle counseling episode was associated with hazard ratios of 1.7 for A1C control (P < 0.0001), 1.3 for blood pressure control (P < 0.0001), and 1.4 for LDL cholesterol control (P = 0.0013).

CONCLUSIONS

Lifestyle counseling in the primary care setting is strongly associated with faster achievement of A1C, blood pressure, and LDL cholesterol control. These results confirm that the findings of controlled clinical trials are applicable to the routine care setting and provide evidence to support current treatment guidelines.

The role of diet and lifestyle in primary, secondary, and tertiary diabetes prevention: a review of meta-analyses

Prevention of diabetes is crucial to lowering disease incidence, and thus minimizing the individual, familial, and public health burden. The purpose of this review is to gather current information from meta-analyses on dietary and lifestyle practices concerning reduction of risk to develop type 2 diabetes. Low glycemic index dietary patterns reduce both fasting blood glucose and glycated proteins independent of carbohydrate consumption. Diets rich in whole-grain, cereal high fiber products, and non-oil-seed pulses are beneficial. Whereas, frequent meat consumption has been shown to increase risk. Regarding non-alcoholic beverages, 4 cups/day of filtered coffee or tea are associated with a reduced diabetes risk. In contrast, the consumption of alcoholic beverages should not exceed 1-3 drinks/day. Intake of vitamin E, carotenoids, and magnesium can be increased to counteract diabetes risk. Obesity is the most important factor accounting for more than half of new diabetes' cases; even modest weight loss has a favorable effect in preventing the appearance of diabetes. Also, physical exercise with or without diet contributes to a healthier lifestyle, and is important for lowering risk. Finally, there is a positive association between smoking and risk to develop type 2 diabetes. As far as secondary and tertiary prevention is concerned, for persons already diagnosed with diabetes, there is limited evidence of the effectiveness of diet or lifestyle modification on glycemic control, but further studies are necessary.

Effectiveness of an intensive nutritional intervention in patients with type 2 diabetes mellitus: results from a pilot study

The aim of this pilot study was to compare the effects of an intensive nutritional intervention with usual care conditions on dropout rate, body weight, lifestyle changes and glycemic control in patients with type 2 diabetes mellitus (T2DM). Thirty outpatients with T2DM but without insulin treatment (mean age: 57 +/- 9 yr) were randomly assigned to one of the two intervention groups: intensive care (IC) or usual care (UC). Patients in the UC group were given advice about dietary and physical activity goals in one consultation session at baseline, while patients in the IC group attended five goal-oriented consultation sessions held approximately every two weeks from baseline onwards. Changes in body weight, T2DM knowledge, dietary intake, physical activity, HbA1c, and percentage of dropouts were evaluated at 1-year follow-up post-intervention. Fifty percent of patients quitted the program and were classified as "dropouts". Program completers were older and included a lower percentage of newly diagnosed T2DM compared with dropouts. A tendency to a negative association between attendance of the IC group and the likelihood of dropping out was found (p = 0.08). No difference was detected between UC and IC groups regarding changes in body weight, HbA1c or other outcome measures, at post-intervention or 1-year follow-up. This pilot study did not confirm advantages of intensive nutritional intervention in T2DM patients in terms of glycemic control, body weight, diet and physical activity. However, the high dropout rate may have hampered its effectiveness.