Low-carb diet/low glycemic - new JAMA study

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http://www.medpagetoday.com/PrimaryCare/Obesity/33484

Yo-Yo Weight Gain Linked to Low-Fat Diet

By , North American Correspondent, MedPage Today

Published: June 26, 2012

Reviewed by Zalman S. Agus,

MD<http://www.medpagetoday.com/reviewer.cfm?reviewerid=30>; Emeritus Professor,

Perelman School of Medicine at the University of Pennsylvania and Dorothy

Caputo, MA, BSN, RN, Nurse Planner

Action Points

ž Note that long-term maintenance of clinically significant weight loss

is difficult for many and in a National Health and Nutrition Examination Survey

only one in six overweight and obese adults report ever having maintained weight

loss of at least 10% for 1 year.

ž Point out that in this study in overweight and obese young adults

following significant weight loss, isocaloric feeding resulted in decreases in

resting energy expenditure and total energy expenditure that were greatest with

a low-fat diet, and least with a very low-carbohydrate diet.

A calorie isn't always a calorie after losing weight, researchers found.

In a prospective study of diets aimed at keeping weight off, a low-fat diet was

associated with a marked decrease in resting energy expenditure compared with

two other regimens that provided the same calories, according to Ludwig,

MD, PhD, of Children's Hospital Boston, and colleagues.

The finding suggests that a low-fat diet after an initial weight loss might

increase the risk of packing the pounds back on, Ludwig and colleagues argued in

the June 27 issue of the Journal of the American Medical Association.

Instead, they argued, people hoping to avoid yo-yoing weight might be better off

to choose a maintenance diet with a low glycemic index.

" Many people can lose weight for a few months, but most have difficulty

maintaining clinically significant weight loss over the long term, " they

commented.

One reason that has been suggested is that losing weight triggers biological

adaptations -- lower energy expenditure and greater hunger -- that induce people

to re-gain the lost pounds.

To test the notion that diets with a low glycemic index might prevent those

changes to some degree, Ludwig and colleagues studied 21 overweight and obese

adults (body mass index ™27 kg/m2), ages 18 to 40.

Participants spent 12 weeks on a run-in diet, aimed at helping them lose at

least 12.5% of their body weight, followed by 4 weeks of weight stabilization.

Then they were randomly assigned, in a three-way crossover, to 4 weeks on each

of three maintenance diets:

ž A low-fat diet with a high glycemic load, in which 60% of energy came

from carbohydrates, 20% from fat, and 20% from protein

ž A diet with a moderate glycemic load, in which 40% of energy came from

carbohydrates, 40% from fat, and 20% from protein

ž A very low-carbohydrate diet with just 10% of energy from

carbohydrates, 60% from fat, and 30% from protein

The last maintenance plan was modeled on the Atkins Diet and had a low glycemic

load.

The main outcome measure was change from baseline in resting energy expenditure,

measured by indirect calorimetry, while secondary outcomes included change from

baseline in total energy expenditure, as well as effects on a range of

biological markers.

On average, Ludwig and colleagues reported, participants lost 14.3 kg (about 31

lbs.) during the run-in phase, or about 13.6% of body weight. Also, their

average body fat percentage, as measured by dual-energy x-ray absorptiometry,

fell from 33.6% at baseline to 29.1% after the initial weight loss.

Energy expenditure during the test phase varied significantly among the three

diets, they found. Specifically:

ž Low-fat diet: Average decrease in resting energy expenditure of 205

kilocalories (kcal) a day versus baseline; average decrease of 423 kilocalories

a day in total energy expenditure

ž Moderate glycemic load diet: Average decreases of 166 kcal and 297

kcal a day for resting and total expenditures, respectively

ž Low-carbohydrate diet: Average, the energy declines were 138 kcal and

97 kcal a day, respectively.

The trend by glycemic load for resting energy was significant at P=0.009, while

the trend for total energy was significant at P<0.001.

The difference in total energy expenditure between the low-fat and the

low-carbohydrate diet - about 300 kcal a day - was roughly equivalent to the

amount of energy expended in an hour of moderate-intensity physical activity.

There were also variations by diet in the various biological markers, but " no

consistent favorable pattern emerged, " Ludwig and colleagues reported.

The results " challenge the notion that a calorie is a calorie from a metabolic

perspective, " the authors argued.

Ludwig and colleagues cautioned that the test periods were relatively short and

it might be hard to extrapolate the results from a controlled feeding study to a

real-world situation in which people select their own diets.

The study had support from the National Institute of Diabetes and Digestive and

Kidney Diseases, the National Center for Research Resources, and the New Balance

Foundation. Ludwig reported receiving grants from foundations for

obesity-related research, mentoring, and patient care, as well as receiving

royalties from a book about childhood obesity.

Primary source: Journal of the American Medical Association

Source reference:

Ebbeling CB, et al " Effects of dietary composition on energy expenditure during

weight-loss maintenance " JAMA 2012; 307:

2627-2634.<http://jama.jamanetwork.com/article.aspx?articleid=1199154>

S. Kalman PhD, RD, FACN

Director, BD - Nutrition & Applied Clinical Trials

Miami Research Associates

6141 Sunset Drive - Suite 301

Miami, FL. 33143

Direct -

Office ext. 5109

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Email: dkalman@...

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