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Old 05-23-2007, 10:06 AM
EricT EricT is offline
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Default Low-Glycemic Load Diet vs. Low Fat Diet w/High Insulin

Low–Glycemic-Load Diet Better Than Low-Fat Diet for Weight Loss in Those With High Insulin Secretions CME
News Author: Shelley Wood
CME Author: Désirée Lie, MD, MSEd
Disclosures

Release Date: May 16, 2007;
from Heartwire — a professional news service of WebMD

May 16, 2007 — Individual differences in insulin secretion may explain why some individuals respond well to either a low-fat diet or low–glycemic-load diet, whereas others do not, a randomized study suggests. The findings imply that a simple, baseline oral glucose tolerance test to assess serum insulin concentration may help clinicians and dieticians choose weight-loss strategies for obese subjects.

Cara B. Ebbeling, PhD, from Children's Hospital Boston, in Massachusetts, and colleagues, report the results of their study in the May 16 issue of JAMA.

"We often ask, why do people succeed with a conventional low-fat diet while others who are following the exact same diet can't keep weight off?" Dr. Ebbeling told heartwire. "Usually we answer this question with something like: 'the ones who succeed are more motivated, or have more willpower, or they're more able to stick with a diet while others are not as motivated.' But this really is not a complete answer to the question. So we sought to determine if biology had something to do with it."

Diet Success
Ebbeling and colleagues randomized 73 obese young adults (aged 18 - 35 years) to a 6-month dietary intervention: either a low–glycemic-load diet (40% carbohydrate, 35% fat, and rich in low–glycemic index foods), or a low-fat diet (55% carbohydrate and 20% fat). At baseline, all subjects were given an oral glucose tolerance test to check for insulin concentration after 75 g of dextrose. Subjects adhered "intensively" to diets for 6 months, then were followed up for an additional 12 months.

For the group as a whole, changes in body weight and body fat percentage at 18 months did not differ between the 2 diet groups; however, when stratified according to baseline glucose tolerance test, subjects with above-median insulin concentration (> 57.5 µlU/mL) lost significantly more weight on the low–glycemic-load diet than they did on the low-fat diet by 18 months. In contrast, subjects with insulin concentrations below median levels (≤ 57.5 µlU/mL) during the baseline glucose tolerance test had similar outcomes, regardless of to which diet they had been randomized.

Table 1. Changes by Diet After 18 Months, Above Median Insulin Concentration Subjects
Outcome Low–Glycemic-Load Diet Low-Fat Diet P
Weight change, kg -5.8 -1.2 .004
Body fat, % -2.6 -0.9 .03


Source: JAMA. 2007;297:2092-2102.

Differences between the diets were seen in effects of the different diets on lipid parameters, regardless of baseline glucose tolerance tests. The low–glycemic-load diet produced significant improvements in high-density lipoprotein (HDL) cholesterol and triglyceride profiles, whereas the low-fat diet produced significantly greater reductions in low-density lipoprotein (LDL) cholesterol levels.

"Regardless of insulin secretion at baseline, the LGL [low–glycemic-load] diet has beneficial effects on HDL cholesterol and triglycerides that were not seen on the LF [low-fat] diet, while LDL cholesterol decreased in the participants in the LF diet, but not the LGL diet," Dr. Ebbeling said. "This is just is speculation on our part, but an LGL diet that also substitutes unsaturated fats for fats may be even more beneficial for everyone, since the beneficial effects on insulin, cholesterol, and triglycerides with the LGL diet were seen regardless of insulin secretion."

Table 2. Lipid Changes by Diet, Entire Cohort*
Parameter Low–Glycemic- Load Diet Low-Fat Diet P
LDL, mg/dL -5.8 -16.3 .03
HDL, mg/dL 1.6 -4.4 .002
Triglycerides, %â€* -21.2 -4.0 .02


*LDL indicates low-density lipoprotein cholesterol; HDL, high-density lipoprotein cholesterol.
â€*mg/dL measurements log-transformed to percentages to reduce skew.
Source: JAMA. 2007;297:2092-2102.

Spikes in insulin concentration after a meal are believed to promote feelings of hunger and can lead to overeating, Dr. Ebbeling told heartwire. "People who are 'high insulin secreters' may be particularly susceptible to weight gain with conventional low fat diets that are higher in carbohydrates." By contrast, low insulin secreters seem to do the same on either the low-fat diet or the low–glycemic-load diet, she continued. "It seems that people who are high insulin secreters may be particularly susceptible to weight gain and may be more challenged to lose weight with a conventional low fat diet."

Of note, in survey questions assessing levels of satisfaction with the diets or with degree of weight loss, or probing ease or palatability of the diets, study subjects responded similarly to both questions.

"From a clinical perspective, our findings provide rationale for individualizing weight loss diets or diet prescription based on an oral glucose tolerance test," Dr. Ebbeling told heartwire.

Clinical Context
According to the authors of the current study, 3 popular diets (low fat, low glycemic load, and low carbohydrate) have received attention recently for addressing obesity, but results of trials have been inconsistent because of different physiologic responses of participants. For example, individuals with different insulin secretion in response to a glucose load may respond differently to a low–glycemic-index diet. According to the authors, benefits of low–glycemic-load or low-carbohydrate diets have been shown in relation to components of the metabolic syndrome.

This is a randomized trial conducted in obese young adults with similar education, treatment intensity, and physical activity to examine whether a low–glycemic-load diet vs a low-fat diet is associated with differential weight and lipid outcomes.

Study Highlights
*Included were adults aged 18 to 35 years with a body mass index of 30 kg/m2 and above and clearance from their clinicians.
*Excluded were current smokers and those with weight exceeding 140 kg, recent weight-loss diet, or diabetes mellitus.
*Prior to randomization, all participants underwent a 75-g glucose tolerance test, and glucose levels, insulin levels at 30 minutes, and lipids were measured.
*The dietary intervention had a 6-month intensive period followed by 12 months of follow-up.
*Measurements were repeated at 6, 12, and 18 months and body weight was tracked.
*Physical activity level and satisfaction with the program were assessed.
*The low–glycemic-load diet (n = 36) comprised nonstarchy vegetables, legumes, healthful nuts, and temperate fruits, limiting intake of high glycemic index foods such as refined grains, starchy vegetables, and fruit juices. 40% of energy was from carbohydrates, 35% from fat, and 25% from protein.
*The low-fat diet (n = 37) comprised 55% carbohydrate, 20% fat, and 25% proteins with an emphasis on low-fat grains, vegetables, fruits, and legumes.
*Participants in both groups received food-choice lists, had serving sizes defined, and received similar nutritional counseling.
*Education was offered in workshops with a total of 23 workshops, 1 private counseling session, and 5 motivational telephone calls for each participant.
*Dietary intake was assessed by the Nutrition Data System for Research Software.
*Dietary variables examined included carbohydrates, fat, protein, and fiber intake.
*Dietary glycemic index and load were quantified by a prespecified method using existing glycemic index values for foods.
*Glycemic load was calculated as the product of the daily glycemic index and total carbohydrate intake and adjusted for energy intake.
*Primary outcomes were weight loss, body fat percentage using dual energy x-ray absorptiometry, and cardiovascular disease risk factors such as lipid profile.
80% were women, 55% were white, mean age was 28 years, mean weight was 103 kg, mean body fat percentage was 41%, and mean blood pressure was 105 mm Hg systolic and 63 mm Hg diastolic.
*Fasting insulin level and trunk fat were higher in those with high insulin levels at 30 minutes after the 75-g glucose load.
*Treatment intensity was similar in the 2 groups, and the 2 groups differed in diet composition as expected.
*Weight loss did not differ for the full cohort of 73 patients.
*Insulin level 30 minutes after the glucose load was a significant modifier of the weight loss effect.
*For those with insulin concentration above the median of 57.5 µIU/mL, the low–glycemic-load diet produced a greater weight loss (-5.8 vs -1.2 kg; P = .004) and body fat percentage (-2.6% vs -0.9%; P = .03) vs the low-fat diet at 18 months.
*The net mean difference was -2.2 kg for each 2-fold increase in insulin concentration at 30 minutes.
*Those with low insulin levels after the 75-g glucose load showed no difference in weight loss between the low–glycemic-load and low-fat diets.
*Body fat percentage decreased more in those with high insulin concentration at 30 minutes for the low–glycemic-load vs the low-fat group.
*The insulin concentration at 30 minutes after a glucose load was not a modifier of lipid effects, blood pressure, fasting glucose levels, or fasting insulin levels.
*Plasma HDL cholesterol and triglyceride levels improved more with the low–glycemic-load diet, whereas LDL cholesterol levels improved more with the low-fat diet.
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If you act sanctimonious I will just list out your logical fallacies until you get pissed off and spew blasphemous remarks.
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