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Effects of a Low-fat diet Compared with a High MUFA Diet on Type-2 Diabetics.

Interesting study as the macronutrient content of the low fat diet (20% fat) is similar to that of the traditional Japanese diet whereas the high fat diet (40% fat) is similar to that of the traditional Mediterranean diet.

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Effects of a low-fat diet compared with those of a high-monounsaturated fat diet on body weight, plasma lipids and lipoproteins, and glycemic control in type 2 diabetes.

ABSTRACT

Background: An important therapeutic goal for patients with type 2 diabetes is weight loss, which improves metabolic abnormalities. Ad libitum low-fat diets cause weight loss in nondiabetic populations. Compared with diets higher in monounsaturated fat, however, eucaloric low-fat diets may increase plasma triacylglycerol concentrations and worsen glycemic control in persons with type 2 diabetes.

Objective: We investigated whether, in type 2 diabetes patients, an ad libitum low-fat diet would cause greater weight loss than would a high-monounsaturated fat diet and would do this without increasing plasma triacylglycerol concentrations or worsening glycemic control.

Design: Eleven patients with type 2 diabetes were randomly assigned to receive an ad libitum low-fat, high-carbohydrate diet or a high-monounsaturated fat diet, each for 6 wk. The diets offered contained 125% of the estimated energy requirement to allow self-selection of food quantity. The response variables were body weight; fasting plasma lipid, lipoprotein, glucose, glycated hemoglobin A1c, and fructosamine concentrations; insulin sensitivity; and glucose disposal.

Results: Body weight decreased significantly (1.53 kg; P < 0.001) only with the low-fat diet. Plasma total, LDL-, and HDL-cholesterol concentrations tended to decrease during both diets. There were no interaction effects between diet and the lipid profile response over time. Plasma triacylglycerol concentrations, glycemic control, and insulin sensitivity did not differ significantly between the 2 diets.

Conclusion: Contrary to expectations, the ad libitum, low-fat, high-fiber diet promoted weight loss in patients with type 2 diabetes without causing unfavorable alterations in plasma lipids or glycemic control.

http://www.ajcn.org/cgi/content/full/80/3/668

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Design
Subjects were fed low-fat or high-mono metabolic diets in random order for 6 wk, and the 2 diets were separated by a 6-12-wk washout period. Both diets were offered at 25% above estimated energy requirement (7) to allow self-selection for quantity of food. Diets were fed by using a 4-d menu cycle. Menus for the 2 diets were similar, with the fat and carbohydrate composition changed by differences in recipes and serving sizes; subjects were thus blinded to dietary treatment, insofar as this was possible. Typical menus for the 2 diets are shown in Appendix AGo, which illustrates the manipulations of the foods that were performed to meet the low-fat and high-mono dietary prescriptions. In general, high-fat items and oils on the high-mono diet were partially replaced on the low-fat diet with fat-free oils and foods higher in complex carbohydrates.

All meals were prepared by the Metabolic Kitchen of the General Clinical Research Center at Oregon Health & Science University. Subjects consumed one meal per day at the Clinical Research Center. The other meals including the weekend meals were packaged for home consumption. Subjects were instructed to eat to satisfaction and return uneaten foods, which were weighed to allow calculation of the total energy intake and nutrient consumption by using a nutrient analysis database (FOOD PROCESSOR NUTRIENT ANALYSIS SOFTWARE, version 6.1; ESHA Research, Salem, OR; 8). Subjects were encouraged to consume their meals on a regular schedule and were instructed to maintain their usual exercise level during the study.

Experimental diets
The low-fat diet provided 20% of energy as fat, and the high-mono diet provided 40% of energy as fat (26% of energy was monounsaturated fat; Table 3Go). The low-fat diet provided 65% of energy as carbohydrates compared with 45% as carbohydrates for the high-mono diet; refined sugar made up 10% of energy intake in both diets. The low-fat diet was higher in fiber and water content, weighed more, and had a lower energy density (kcal/g diet) than did the high-mono diet. Although both diets were low in saturated fat, the low-fat diet was lower than the high-mono diet in saturated fat and cholesterol. The difference in saturated fat and cholesterol between the 2 diets was intentional, in that we wished to study the effects of a diet in its entirety (low-fat compared with high-mono), rather than the effects of individual dietary components. A low-fat diet will generally be lower in saturated fat and cholesterol and higher in dietary fiber than will a high-mono diet, so that the composition of the 2 diets in our study likely mirrored the composition of these diets as they would be eaten in the "real world."

considering:

1. It's all processed food so they could blind which is not very good
2. they didn't even state which mono-unsats they used
3. 25% overconsumption was required
4. low fat diet had much more fiber
5. refined sugar was 10% in both diets

etc.

Ewwww...

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Originally Posted by Steven Low (Post 71647)

considering:

1. It's all processed food so they could blind which is not very good.

I would assume this was done to prevent the subjects knowing the fat content of the different diets as this may have influenced the amount they ate.

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2. they didn't even state which mono-unsats they used.

According to Appendix A they used olive oil, high–oleic acid safflower oil and safflower oil margarine for both diets.

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3. 25% overconsumption was required.

No, an extra 25% was offered but it's consumption was not required -

"The diets offered contained 125% of the estimated energy requirement to allow self-selection of food quantity"

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4. low fat diet had much more fiber

Unavoidable and addressed by the author -

"A low-fat diet will generally be lower in saturated fat and cholesterol and higher in dietary fiber than will a high-mono diet, so that the composition of the 2 diets in our study likely mirrored the composition of these diets as they would be eaten in the "real world.""

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5. refined sugar was 10% in both diets

Not ideal I agree but it does reflect the real world diets of overweight diabetics and as it was the same for both diets it wouldn't have influenced the results.

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Ewwww...

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RESULTS

Weight change and energy balance

The most striking finding in this study was that the ad libitum low-fat, high-fiber diet induced a significant weight loss, whereas the high-mono diet did not. The statistically significant time x diet interaction for the body-weight changes indicated a differential response of body weight to the 2 diets (Table 2Go). Further analysis using Tukey’s multiple comparisons procedure indicated that weight loss was statistically significant only during the low-fat diet (–1.53 ± 1.21 kg; P < 0.001). Body weight decreased ≥1.0 kg in 8 of the 11 participants during the low-fat diet and in only 3 of the 11 subjects during the high-mono diet. Subjects were offered a mean of 3555 kcal/d during both diets (Table 3Go), which is 25% above the eucaloric energy requirement of 2848 ± 281 kcal/d. The subjects consumed 212 fewer kcal per day during the low-fat diet than during the high-mono diet (P < 0.02). The predicted difference in the weight loss between the 2 diets, based on the 212 kcal/d difference in energy intake, was –1.15 kg [assuming a total relative caloric deficit on the low fat diet of 212 kcal x 42 d = 8904 kcal, and a deficit of 3500 kcal = 1 lb (2.2 kg)]. The predicted differential weight loss was comparable to the observed difference of –1.06 kg between the 2 diets.

Weight loss was the only statistically significant difference in outcome, yet was accounted for in the calorie intake.