A high-protein diet may be better for keeping weight off once it's been lost, according to early results from a European study.

In these preliminary findings, researchers compared high and low protein diets with those based on the glycemic index (GI).

High protein diets include lots of meat, fish, eggs, beans and lentils.

High-GI foods are carbohydrates, such as potatoes or white bread, that are digested quickly, leading to a rapid release of glucose (sugar) into the bloodstream. Low-GI foods, such as many raw fruits and vegetables, are digested slowly and allow for a more gradual release of glucose.

Low-GI diets are supposed to help with weight control by making people feel fuller for longer and by reducing cravings for sweets. They also help diabetics control blood sugar.

In the study, more than 200 adults first completed a weight-loss program that required them to lose at least 8 per cent of their body weight. They were then assigned to follow one of five diets for six months:

  • Diet 1: low protein, low GI = 12 per cent of energy from protein, 55 to 60 per cent of energy from low-GI carbohydrates.
  • Diet 2: low protein, high GI = 12 per cent of energy from protein, 55 to 60 per cent of energy from high-GI carbohydrates.
  • Diet 3: high protein, low GI = 25 per cent of energy from protein, 45 to 50 per cent of energy from low-GI carbohydrates.
  • Diet 4: high protein, high GI = 25 per cent of energy from protein, 45 to 50 per cent of energy from high-GI carbohydrates.
  • Diet 5: control diet = balanced diet based on general dietary guidelines.

After six months, the researchers found that subjects on Diets 1, 2 and 5 re-gained an average of four to six pounds, while subjects on diets three and four only regained an average of less then two pounds.

While the study subjects were not specifically on any of today's popular diets, the findings seem to indicate that the high-protein Atkins or Zone diets are better for weight loss than newer, trendier options such as the GI or South Beach diets.

The results were presented Wednesday by study coordinator Professor Arne Astrup of the University of Copenhagen at a Pre-Congress of Obesity Satellite Symposium in Geneva, Switzerland.

The study, known as Diogenes, is designed to analyze which diets are best for weight control. It is also investigating how a high-protein diet influences weight loss and how genetics may make some diets better for some and not for others.

The final results will be presented next spring.

"I think the message is following diets with low glycemic index might be good for type 2 diabetics who are concerned and need some control of their blood sugar and it might have a slight effect on the bad LDL cholesterol," Astrup told CTV.

"But in terms of weight loss and weight regulation, the glycemic index does not play any role, so there is no reason really to waste efforts and money on that for body weight regulation."

Dr. Yoni Freedhoff of the Bariatric Medical Institute said that because protein in fact makes people feel full for longer, it makes sense that it would be easier to lose weight by following a high-protein diet.

"We certainly recommend that people have protein with every single meal or snack to minimize hunger, and to eat every two to three hours," Dr. Freedhoff said.

"It's important to not be hungry to be in control."

Ottawa resident Cynthia Rose learned to successfully keep off the 30 pounds she had lost by eating three meals and three snacks a day, and having some protein every time.

"I wasn't having protein for breakfast, and this made a big difference. Once I incorporated a handful of almonds at coffee time at 10, and made sure I had protein at breakfast, it really helped," said Rose.

With a report by CTV's medical correspondent Avis Favaro and producer Elizabeth St. Philip.

Abstract:

Weight loss maintenance on ad libitum diets varying in protein content and glycemic index: first results of the DIOGENES highly-controlled shop-based intervention.

van Baak, MA, Larsen, TM, Jebb, SA, Kafatos, A, Pfeiffer, A, Martinez, JA, Handjiev, S, Kunesova, M8, Astrup, A, Saris, WHM

AIM To study the effects of protein content and glycemic index (GI) of the diet on weight loss maintenance during a 6-month highly controlled shop-based dietary intervention in 2 centers.

DESIGN After an 8 week low calorie diet (body weight (BW) loss 11�3%), 263 adults (106 men, 157 women; BW 99.8�15.6 kg, BMI 33.5�4.3 kg/m2, age 42�6 y) were randomized to 5 ad libitum diets for 6 months: high protein/low GI (HP/LGI), HP/high GI (HP/HGI), low protein/high GI (LP/HGI), LP/low GI (LP/LGI) and control diet. Aim was a difference in protein intake of >10 energy% and in GI of >10 units. Foods were provided for free and registered through a shop system.

RESULTS 205 subjects (=78%) completed the 6-month intervention. Their BW increased 1.5�4.6 kg or 16.0�40.9% of initial weight loss (P<0.001). Weight regain across diets (in kg and as % of initial weight loss) was 2.1�3.9 and 19�35 (LP/LGI), 2.8�3.5 and 26�37 (LP/HGI), 0.8�4.3 and 8�39 (HP/LGI), 0.3�6.4 and 7�52 (HP/HGI), and 1.9�4.3 and 22�37 (control). Factorial ANOVA with BMI, gender and initial weight loss as covariates showed a significant main effect of protein content (P = 0.006 resp. 0.009), but no main effect of GI or interaction between protein and GI.

CONCLUSION A higher protein content of the diet improved weight loss maintenance, GI did not modify this effect. Funded by the EU contract nr: Food 2005-CT-513946