Does "Diet" Fail?
Marion J. Franz, MS,
RD, CDE, Joyce Green Pastors, MS, RD, CDE,
"Diet failure" or "when diet fails" are common expressions used by health care professionals when oral medications or insulin need to be added to diabetes therapies. Unfortunately, patients are often blamed for "diet failure"if they had just lost weight, they would not need medications or insulin.
But what exactly has failed? Is it the "diet," or is it instead the treatment recommendations (e.g., no referral made for medical nutrition therapy [MNT], inadequate support or ineffective recommendations given, medications not added when necessary) that have failed? Or, is it the pancreas that has failed?
This article examines the following questions:
MNT and the
Throughout the study, dietitians in each center worked closely with the diabetes team, and nutrition therapy underpinned all treatment modalities.1 The food intake of a random subgroup of 120 patients in five centers was recorded in 1990.4 Total food energy was 1,650 kcal/day with ~43% from carbohydrate, ~21% from protein, and ~37% from fat. Men reported a larger average caloric intake than women (~1,800 vs. ~1,450 kcal/day), and obese and nonobese individuals reported similar caloric intakes. Many reported making positive changes in their food choices, for example, 6070% reported reducing their intake of high-fat foods. No differences were noted in the food profiles reported by patients allocated to diet, oral medications, or insulin therapy. In addition, no differences were seen in food profiles between clinical centers, suggesting that well-recognized regional food variations in the United Kingdom had been overcome by the nutrition recommendations given to the patients.1
During the nutrition run-in, patients lost an average of 3.5 kg (8 lb). The response to the nutrition intervention showed a large initial decrease in fasting plasma glucose over the first month and a slower decrease in the next 2 months, despite a continued weight loss.5 This suggests that the initial glucose response was at least as much a response to the decrease in caloric intake as it was to the decrease in body weight. Fasting plasma glucose levels <6.0 mmol/l (110 mg/dl) were only maintained in patients who continued a restricted caloric intake. In patients who increased their caloric intake, fasting plasma glucose levels increased even if the weight loss was maintained. UKPDS researchers concluded that the reduction of energy intake was at least as important as, if not more important than, the actual weight lost in determining the fasting plasma glucose.5
Patients assigned to the conventional blood glucose control group were able to maintain their body weight ~2 kg (4 lb) below their starting values. Patients in the intensive treatment group did have a significant increase of ~1.5 kg (3 lb) above their starting weight, especially those patients assigned insulin who gained 4.0 kg (9 lb) more than those assigned conventional therapy.3 Metformin therapy in overweight, conventionally treated patients was weight-neutral.1 A quality-of-life study that was integral to the UKPDS showed that therapeutic regimens had no effect on quality of life.6
So, if MNT did not fail, why did blood glucose levels increase over time? One of the major lessons learned from the UKPDS is that type 2 diabetes is a progressive disorder, and therapy needs to be intensified over time. As the disease progressed, MNT alone was not enough to keep the majority of patients' HbA1c level at 7%. Medication(s) and, for many individuals, eventually insulin needed to be added to the treatment regimen. It was not the diet failing (or eventually the oral medications failing). It was instead the pancreas failing to continue producing the insulin needed to maintain adequate glycemic control. However, without continued nutrition interventions, fasting plasma glucose levels and HbA1c levels would have increased even more.
In a discussion of the UKPDS findings, R. Holman, Oxford, U.K., made the following observations. Interestingly, the greatest HbA1c reduction was the fall of 2% during the first 3 months with intensive diet and 5% weight loss. Monotherapy in the intensive group further reduced HbA1c by 0.9%. The subsequent progressive increase in glucose is not a therapy-specific problem, since all drugs were similar in glucose control. "The real problem," he stated, "is the progressive decrease in -cell function from 53 to 28% during the first 6 years of treatment." He insisted that "we are now duty-bound to explain this to our patients at the outset ... and not to castigate them because they failed to diet."7
Should MNT Focus on
Blood Glucose Control or Weight Loss?
Weight loss is not always the answer to glucose control. Watts et al.9 examined predictors of improvement in glycemia after weight loss of at least 9 kg (20 lb) in 135 obese people with type 2 diabetes. Fifty-five (41%) had mean plasma glucose levels <120 mg/dl after weight loss, with the major improvements occurring after losses of only 24.5 kg (510 lb). But 80 of the patients (59%) actually had somewhat higher glucose levels after a 9-kg (20-lb) weight loss than before.
The authors concluded that individuals who have lost 4.5 kg (10 lb) without achieving blood glucose levels <180 mg/dl are unlikely to improve with further weight loss and should be considered for treatment with insulin or oral agents. They speculated that those who benefited from weight loss were hyperglycemic because of relatively more insulin resistance, and those who did not respond to weight loss had hyperglycemia because of more severe insulin deficiency. In clinical practice, how long patients have had diabetes before being diagnosed is often unknown. If the onset of type 2 diabetes on average is ~10 years before clinical diagnosis,14 at this point, it may be too late for weight loss to help.
Does this mean that by the time patients are diagnosed it is already too late for nutrition therapy to be helpful? In a clinical trial comparing basic nutrition care (one visit with a dietitian), intensive nutrition care (two or three visits with a dietitian), or no nutrition intervention in patients with type 2 diabetes, the average duration of diabetes was 4 years, and the nutrition interventions focused on glycemic control rather than weight loss. On average, the two groups receiving nutrition care had a 12% decrease in HbA1c levels and fasting plasma glucose (FPG) levels decreased by 50100 mg/dl. Patients receiving intensive nutrition care at 6 months had a mean FPG value 10.5% lower than that at entry, whereas those receiving basic nutrition care had values 5.3% lower.
The subgroup of patients with an average duration of diabetes <1 year had the greatest improvement in glucose control with the implementation of nutrition therapy. However, even in the subgroup of patients who had an average diabetes duration of 45 years and were on oral medications, mean HbA1c decreased from 8.8 to 7.5% without change in medications.15
Furthermore, the results of the nutrition intervention were evident by 6 weeks to 3 months after the initial visit. This is the point at which patients and their health care teams should decide whether MNT alone is succeeding or whether medical therapy (medication) is needed. Unfortunately, patients often receive no MNT, or if they do, they may go for months or years before anyone looks at and acts on the intervention outcomes.
MNT is the process of providing nutrition care and, for diabetes, includes recommendations for both food/nutrition and physical activity. It includes assessment, intervention, goal setting, and evaluation and is essential for improved metabolic control. However, traditional advice to patients with type 2 diabetes has focused largely on the need to lose weight by following a low-calorie "diet sheet." And although we would all like to be able to help patients succeed at losing weight and maintaining weight loss, recidivism continues. Research has shown little long-term success for weight-loss maintenance.16 New research is helping to clarify why weight-loss maintenance is difficult17-19 and identify the psychological consequences associated with the dieting process.20
Although morbid obesity (BMI >40) is a predictor of premature death,21 in World Health Organization Multinational Studies, obesity (BMI >29 with type 2 diabetes and >26 with type 1 diabetes) was not associated with mortality risk.22,23 In the Wisconsin Epidemiologic Study, obesity (BMI >31) also was not related to the development of micro- or macrovascular complications of diabetes.24 In another study,25 obesity (BMI >28), and in the UKPDS,26 obesity (BMI >29), was not associated with an increased risk of coronary artery disease. However, many of the long-term problems associated with type 2 diabetes are associated with glycemic control.3 Furthermore, it has been shown that it is better to be fit than thin to decrease mortality risk from chronic diseases.27 As in the UKPDS, research also suggests that even if weight loss is maintained over 12 months in subjects with type 2 diabetes, initial improvements in HbA1c resulting from weight loss are not always maintained.28
Therefore, the focus of MNT for individuals with type 2 diabetes needs to be on lifestyle strategies that will improve the metabolic abnormalitiesglucose, lipids, and blood pressureassociated with the disease. Moderate weight loss is one of several strategies that can be helpful, but it should not be the primary focus of MNT. Food choices, especially portion sizes, have been shown to be of equal importance. Obesity is associated with the development of chronic diseases such as type 2 diabetes. However, the prevention of chronic diseases requires a better understanding of what controls appetite and better tools, including medications, to assist with weight loss or at least to prevent weight gain.
A modest sustained weight loss has been shown to be beneficial in reducing the risk of diabetes in overweight individuals. Data from the Framingham Study revealed that overweight subjects who lost >1 lb per year during the initial 8-year period and kept the weight off during the second 8-year period and those who continued to lose weight during the second 8-year period had a substantially lower long-term risk of developing diabetes than did those with a stable weight.29 Results from the Diabetes Prevention Program will provide more complete answers regarding whether weight loss can prevent or delay the onset of diabetes.30
of Role Responsibilities
A major responsibility of referring providers is to provide dietitians with the necessary referral dataespecially lab dataand, when needed, to adjust medications based on the MNT outcomes. A major responsibility of dietitians is to determine and implement appropriate nutrition prescriptions and to make recommendations to referring providers based on the nutrition intervention.
The nutrition prescription must be based on the lifestyle changes that patients are willing and able to makenot on predetermined calorie levels and percentages of carbohydrate, protein, and fat. The focus of nutrition interventions is to assist and facilitate patient lifestyle and behavioral changes. And, just as it is important for patients to continue to receive medical care from their primary provider, it is also important that patients receive continued nutrition care from their dietitian.
Advice for Patients
Patients also need to understand the progressive nature of type 2 diabetes. It is probably not realistic to tell patients who have had diabetes for 812 years that they will not need insulin if they can just lose weight. As the disease progresses, health care professionals should avoid blaming the diet and the patient and move toward improving diabetes control by combining MNT with diabetes oral medications as well as with insulin when needed.
Many dietitians have found it helpful to prioritize nutrition advice. Patients need to know how foods affect blood glucose levels and what foods, portion sizes, and number of servings they should select for meals or snacks. Although many factors affect the glycemic responses to food in people with type 2 diabetes (e.g., the food form alters the postprandial glycemic response as well as the severity of glucose intolerance), it is primarily the total amount of carbohydrate eaten that affects post-meal blood glucose levels. A good starting point is to teach patients which foods contain carbohydrate (starches, fruits, starchy vegetables, milk, and sweets), that one portion is the serving size containing 15 grams of carbohydrate, and how many servings (or grams of carbohydrate) they should eat at each meal or for snacks.32,33 Emphasize the importance of including carbohydrate-containing foods in a healthful diet. Our bodies need the nutrients found in whole grains, fruits, vegetables, milk, and other carbohydrate-containing foods.
Patients also need to learn about fat, calories, eating out in restaurants, consuming alcohol, and numerous other topics, but these can be discussed at follow-up sessions. Thus, continued nutrition care is essential.
Physical activity also needs to be encouraged. Exercise has the potential to improve glucose tolerance by reversing or decreasing insulin resistance.34,35 Exercise improves insulin sensitivity by activating intracellular GLUT4 transporters, thereby improving peripheral glucose uptake. It also suppresses hepatic glucose production. This can occur even without changes in body weight, body fat content, or fitness as measured by maximal oxygen uptake (Vo2max).36
Because enhanced insulin sensitivity is lost within 4872 h after exercise, regular physical activity is needed to produce continuing insulin sensitivity.37 Although aerobic exercise is recommended, muscle-strengthening activities can also contribute to improved glucose control.38 Studies suggest that exercise is most effective in people with impaired glucose tolerance or with fasting blood glucose levels <200 mg/dl.39
At follow-up sessions, pre- and post-meal blood glucose monitoring data can be used to determine how much carbohydrate and/or how many total calories patients can tolerate at a meal. Blood glucose monitoring data also help patients understand the impact of physical activity on blood glucose levels. Furthermore, patients can also report what changes are realistic for them to make long term. This information can be used to determine whether medication needs to be added or adjusted.
Patients need to know their blood glucose goals, what to do with the blood glucose monitoring information, and when to call if food and activity changes alone are not helping them achieve their target blood glucose goals. Dietitians or other diabetes educators can evaluate the outcomes from lifestyle changes and contact referring providers if changes in medications are necessary.
Teaching people carbohydrate counting and fat modifications, encouraging physical activity, and keeping food and blood glucose records are essential. However, MNT needs to be integrated into the total diabetes management plan, and all health care providers must give similar nutrition messages.
As the disease progresses, MNT needs to continue as one component of the combination treatment of type 2 diabetes. Not everyone responds to MNT alone, just as not everyone responds to only one type of medication. Both type 2 and type 1 diabetes require MNT to achieve optimal control. It can work as monotherapy or in combination with other medications, and the combination of healthful food choices and physical activity have the added benefit of improving overall health.
Table 2 provides a summary of lessons learned from diabetes MNT research.
Health care professionals and patients need to know when to expect to see results from lifestyle changes and what outcomes to expect from MNT. As the disease progresses, they need to stop blaming either the diet or the patients for failing. These are some of the lessons learned from the UKPDS and other outcomes research.
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Marion J. Franz, MS, RD, CDE, is a nutrition/health consultant in Minneapolis, Minn. Joyce Green Pastors, MS, RD, CDE, is a diabetes nutrition specialist at the Virginia Center for Diabetes Professional Education in Charlottesville, Va. Hope Warshaw, MMSc, RD, CDE, is a diabetes educator and freelance writer in Alexandria, Va. Anne E. Daly, MS, RD, LD, CDE, is Director of Nutrition & Diabetes Education at the Springfield Diabetes & Endocrine Center in Springfield, Ill.
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