November 29, 2022, 8:50 a.m. Michael Devitt — Findings from two new studies can help family physicians counsel their patients with type 2 diabetes about specific diet and lifestyle changes that show positive effects on insulin resistance and hemoglobin A1c levels.
The studies, published in the open access journals Diabetologia and JAMA Network Open, may prove useful in the prevention and treatment of type 2 diabetes.
“The results of these studies will give family physicians added tools to help combat the growing number of Americans with type 2 diabetes,” said Beulette Hooks, M.D., medical director of the family medical clinic at Martin Army Community Hospital in Fort Benning, Ga. “Many patients do not want to use medications to treat diabetes, so this will give them a chance to lower the A1c in a more natural way.”
In the first study, researchers analyzed the physical activity levels 775 adults who participated in an obesity study. Researchers continuously monitored the participants on four consecutive days and categorized them as being most active in the morning, afternoon or evening, or having an even distribution of moderate to vigorous physical activity throughout the day.
Compared with adults who had an even distribution of physical activity, insulin resistance was reduced by up to 18% in those who were most physically active in the afternoon and up to 25% in those who were most active in the evening. There was only a 3% reduction in insulin resistance among those who were most active in the morning.
Based on these findings, the researchers said “the time of the day when physical activity is performed may be relevant for metabolic health and may be considered during lifestyle advice,” while also acknowledging that the timing of exercise “is a relatively unexplored field in human studies.” While they did not consider whether physical activity later in the day directly reduces the risk of diabetes, they did call for further studies to “assess whether timing of physical activity is indeed important for the occurrence of type 2 diabetes.”
In the second study, researchers randomly assigned 150 people with elevated untreated hemoglobin A1c levels of 6% to 6.9% into two groups. One group maintained a usual diet, received written information on dietary advice from the Department of Agriculture and had the option to participate in monthly educational sessions unrelated to diet. The other group participated in a six-month dietary intervention program that targeted a net carbohydrate intake of less than 40 grams per day for the first three months, then less than 60 grams per day for the next three months, with an emphasis on high-fiber carbohydrates. Participants in the intervention group also received behavioral counseling and a handbook with dietary guidelines and recipes.
Compared with a usual diet, participants in the dietary intervention group had significantly larger decreases in A1c levels. This group also had significantly greater decreases in fasting plasma glucose, body weight and systolic blood pressure levels. While adverse event rates were similar among groups, significantly more individuals in the intervention group reported muscle cramps throughout the study period.
Because of the study design, the authors said they could not determine the effects of reducing carbohydrate intake on A1c levels independently of caloric restriction and weight loss. Nevertheless, they suggested that a low-carbohydrate diet “may be an option for people with or at high risk of type 2 diabetes to improve glycemic and other markers, and should be studied further and over longer time periods in other populations and settings.”
Hooks said that the studies offer good information in two areas where family physicians often try to engage patients when they are first diagnosed with prediabetes and early type 2 diabetes.
“Family physicians can let their patients know studies have been done on timing physical activities and how a sustained low-carbohydrate diet can help lower their A1c, thus preventing end-stage organ damage from type 2 diabetes,” she said, adding, “If FPs can help prevent patients being treated for prediabetes, with the results of the two studies we could hopefully prevent them from getting type 2 diabetes.”
Diabetes is the seventh-leading cause of death in the United States, and the leading cause of kidney failure, adult blindness and lower-limb amputation. Roughly one in 10 Americans has diabetes according to the current clinical standards, and one-fifth of people who meet the criteria for diabetes don’t know they have it, which makes early detection and management crucial.
To help family physicians provide optimal care to patients with diabetes, the AAFP has assembled a comprehensive collection of resources on the topic. Many of these can be found on the Academy’s Diabetes: Clinical Guidance and Practice Resources webpage, which is continuously updated. Among other things, the page includes links to guidelines on diabetes screening, treatment and management (including the AAFP's own clinical preventive service recommendation on screening in adults); practice management recommendations; implementation tools and considerations; and clinician and patient educational materials.
In addition, Hooks recommended that FPs visit familydoctor,org, which contains entries written for patients on diabetes symptoms, diagnosis and treatment; diabetes and nutrition; diabetes and exercise; prediabetes and many other topics.