01 June 2012

Making a limited variety diet work

Reducing people's options for junk foods gets them to cut back on the amount of kilojoules they take in from junk food, but it doesn't help them to lose weight, a study shows.


Reducing people's options for junk foods gets them to cut back on the amount of kilojoules they take in from junk food, but it doesn't help them to lose weight, according to a new study.

"Limiting variety was helpful for reducing intake for that type of food group, but it appeared that compensation occurred in other parts of the diet," said Hollie Raynor, a professor at the University of Tennessee and the lead author of the study.

In other words, people tend to make up for the fewer kilojoules in the restricted food group by eating more kilojoules from other types of foods.

The results offer a cautionary note to dieters limiting their food variety, such as on a low-carbohydrate diet, to be watchful of all kilojoules coming in and not just those from the targeted food group.

Change lifestyle to lose weight

Previous studies have shown that people with less variety in their diets tend to be more successful in losing weight and keeping it off, said Raynor.

She said she wanted to see if restricting the options for high-kilojoules, low-nutrition foods, such as ice cream, cookies and chips, could help people lose weight.

She and her colleagues asked 200 overweight and obese adults to make lifestyle changes aimed at losing weight.

These included participating in regular group meetings that discussed healthy behaviours, eating a kilojoule-reduced diet and increasing physical activity.

Half of the people in the study, published in the American Journal of Clinical Nutrition, were also told to limit the junk food in their diet to just two options.

The idea is that monotony on the menu leads to a lack of interest in the food.

"It's clear the more variety you have, the more you eat," said Alexandra Johnstone, a researcher at the University of Aberdeen in Scotland, who was not involved in the research.

Portion sizes

The study lasted 18 months, and the people in the limited junk food group managed to eat fewer types of treats each day – two to three – than the other group – around four. They also ate fewer kilojoules each day that came from junk foods.

At six and 12 months into the study, the people in the low-variety group ate about 100 fewer junk food kilojoules each day than the other group and 80 fewer junk food kilojoules each day by the end of the study.

Both of the groups ate fewer total kilojoules over the course of the study than at the beginning and were able to lose weight.

But the overall reduction in kJ and the weight loss – about 4.5kg – were the same in each group, demonstrating that restricting the junk food choices did not offer any extra benefits over the lifestyle changes that the people had made.

Reduce variety in diet

"It makes sense to try and reduce the amount of variety in the diet, but human beings enjoy eating, so they will find other food components to consume than the ones that are being limited," Johnstone told Reuters Health.

Johnstone said that to make a limited variety diet work, it will be important to also limit the portion sizes at meals. Raynor said it wasn't apparent where the compensation was occurring in the other food groups.

She said there's a need for more research to understand how people's behaviours change when they're trying to limit, say, carbohydrates or sugar-sweetened beverages.

"Do they compensate or go, 'OK, I'm just consuming fewer kilojoules.' It is an area we're developing a better appreciation for," she said.

Raynor said the message to dieters is that if they are trying to lose weight by restricting the variety in their food choices, they should be aware of their other food choices so that it doesn't undermine their efforts.

(Kerry Grens, Reuters Health, June 2012) 

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