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09.02.2013

Why pistachio nuts work in a weight-loss diet (and pretzels don't)

If you are trying to lose weight by following a not-too-strict diet, a bowl of salty snacks can undermine your success. Pistachio nuts are a better choice, according to an article that researchers at the UCLA Center for Human Nutrition published in the Journal of the American College of Nutrition.

A calorie is not a calorie
Most scientists will tell you that you lose weight by consuming fewer calories than you burn, and that's the end of the story. But a growing minority say that the type of calories consumed is also important. Their motto is "A calorie is not a calorie". The more serious popular weight loss diets are partly based on this principle.

In the new appriach the wrong kind of calories tend to come from quickly absorbed carbohydrates. Epidemiologists notice that people who consume carbohydrates in the form of crisps, potato products and soft drinks put on weight more easily than the clever people who manage to eliminate these foods from their diet.

Salty snacks like pretzels also contain these extra-fattening carbohydrates. The nutritional values are reproduced below on the right.

Study
The researchers wanted to know what the best kind of snack is for dieters: food containing healthy fats or food with a high carbohydrate content. Studies show that a diet containing lots of healthy fats in the form of olive oil or nuts is healthy, but because 'fat' has a bad name, many dieters avoid all foods that contain fat. The researchers' intention was to find out whether this is a correct assumption.

The researchers put two dozen test subjects on a diet that provided 500 kcals fewer per day than they burned for a period of 12 weeks. Every evening the subjects ate 220 kcal in the form of 56 g salted pretzels. An equal-sized group of subjects followed an identical diet, but ate 240 kcal in the form of 53 g pistachio nuts every evening. The nutritional values are shown above on the left.

Results
The researchers discovered that the cardiovascular health improved in the pistachio group. The concentration of triglycerides [in other words fat] in their blood went down, as you can see in the figure below. Click here for the full table.

The figure above shows how the subjects' BMI changed throughout the 12 weeks that the experiment lasted. In the pretzel group the average BMI dropped from 30.9 to 30.3; in the pistachio group the drop was from 30.1 to 28.8.

In terms of kilograms this means: the pistachio group went from 86.0 to 82.3 kg, losing 3.7 kg; the pretzel group went from 85.5 to 92.8 and lost 2.7 kg. So the pistachio group lost a kilogram more than the pretzel group.

Source:
J Am Coll Nutr. 2010 Jun;29(3):198-203.

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