Lifestyle changes through counseling and follow-up in first-degree relatives of patients with type 2 diabetes - Diabetes Mellitus

Nutrition Research Newsletter, August, 2003

Type 2 diabetes is increasing worldwide. There is a strong need for prevention strategies to slow this development, targeting both the population level and individuals at increased risk. Many of the known risk factors for type 2 diabetes are related to lifestyle. Established factors include being overweight, physical inactivity, and smoking. Dietary factors, including total fat, saturated fat, and the glycemic index of the diet, have been suggested to influence insulin sensitivity. During the last decade, several studies have investigated lifestyle interventions to prevent type 2 diabetes and modification of factors related to the insulin resistance syndrome. Most of these studies focused on high-risk groups such as people with obesity, impaired glucose tolerance (IGT), or even newly diagnosed type 2 diabetes.

First-degree relatives of people with type 2 diabetes have an increased risk of developing the disease compared with people without diabetes heredity. They show signs of insulin resistance and insufficient insulin secretion despite normal glucose tolerance. Early prevention of diabetes could be of great importance in these individuals. However, little is known about the effectiveness of lifestyle intervention in this, presumably motivated, target group. Weight reduction cannot always be a primary goal because these individuals are not necessarily overweight. A controlled lifestyle intervention trial (pilot project) is ongoing in Goteborg, Sweden, aimed at improving metabolic features related to insulin resistance by targeting several lifestyle components that may influence insulin sensitivity. The aim of this report is to: a) describe the two lifestyle prevention strategies tested in non-diabetic first-degree relatives of patients with type 2 diabetes, and b) to examine the short-term effects on nutrient intake, physical activity pattern, and body weight.

Individuals (between age 25 and 55 years) with two first-degree relatives (parents or siblings) or one first-degree and at least one second-degree relative (grandparents or parents' siblings) with type 2 diabetes were recruited for the study. The goal was to include 90 participants (allowing for a dropout of 15), which in turn would be allocated to one of three groups: diet group (D), diet and exercise group (DE), and control group (C). Baseline data were collected during two visits. At the first visit, screening with the oral glucose tolerance test (OGTT) (75 g glucose) was performed and dietary data were obtained. During the second visit, fasting blood samples and data on physical activity were collected. After baseline examination and randomization, the control group received a letter informing them that they should continue their normal lifestyle and would receive lifestyle intervention one year later.

With a typical Swedish diet as the starting point, goals were devised to achieve a dietary composition based on the Nordic Nutrition Recommendations (NNR) for the Diet Group (D). Dietary advice aimed at reducing saturated fat (goal 10% of energy), increasing intake of monounsaturated fat (goal 10% to 15% of energy) and n-3 fatty acids (goal 1% of energy) from fatty fish and from vegetable origin, increasing intake of vegetables (one third of lunch/dinner plate), increasing fruits and soluble and insoluble fiber.

One additional goal was established for this study: Increase intake of low-glycemic index (GI) foods and reduce intake of high-GI foods. This goal was added because a diet with a high glycemic load has been suggested to increase risk of type 2 diabetes. It was clearly stated at counseling that those who regularly had been taking n-3 capsules were recommended to continue doing so throughout the study period, while those who did not take such supplements were asked to not begin.

Two dietary education sessions were held 1 to 2 weeks apart at study start. Counseling was performed in a group setting and participants were requested to bring a relative or a person in the same household, preferably the person who prepares the meals. Group size varied from 3 to 11 participants. Occasionally, counseling had to be performed individually. Each occasion lasted between 1 hr to 2 hr and consisted of three elements. First was a theoretical part with presentation of dietary advice and background. Examples of recommended foods were then served (fatty fish, low-fat sausage, low-fat cheese, pasta salad with kidney beans and dressing based on canola oil [rapeseed oil], low-fat margarine, different types of kernel-based sourdough bread, rice with low GI, and beans/lentils). There was time for questions and a discussion about food choice. Additional topics for discussion included meal pattern, importance of regular meal frequency, and potential side effects of increased fiber intake. All counseling was performed by a dietitian.

The Diet and Exercise group (DE) received exactly the same dietary counseling as the diet group. In addition, a group discussion was included about the benefits of physical activity, especially on glucose metabolism. The goal, based on NNR, was to increase physical activity by walking or more intensive activities for at least 30 minutes, four to five times per week, regardless of present activity level. Alternatively, they could increase intensity if increased frequency was not possible. Suggestions on how to increase physical activity were discussed and participants were requested to decide for themselves how to achieve the goal.