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High-protein diets

The recent fashion for high-protein diets has seen many people removing carbs from their diets. Is a high-protein diet a good idea?

Any 'diets' that completely eliminate carbohydrate- containing foods or whole food groups are not recommended for long-term weight loss or health.

To lose weight, you need to create an energy deficit in the body by taking in fewer kilojoules than your body needs for weight maintenance.

To meet nutritional requirements we need to eat a variety of foods from each of the food groups every day: breads and cereals; milk and dairy foods; vegetables and fruit; protein foods.

Very high-protein, low-carbohydrate diets are based on the assumption that because there are no carbohydrates to feed glucose into the blood, there is less usage of the hormone insulin which manages blood glucose levels (and also triggers fat storage).

Although this appears to make sense, in fact:

  • Studies have shown that long-term weight loss from very-high-protein versus high-carbohydrate or low-fat diets are similar, and successful weight loss depends on a sustained energy deficit rather than higher or lower intakes of certain macronutrients.
  • Very-high-protein diets are hard to sustain in the long term because of the restricted food choices; drop out rates for extreme diets are very high.
  • Very-high-protein diets can also be high in saturated fat if the wrong choices are made.
  • Animal protein foods do not contain fibre, which is essential for bowel health.
  • If you eat more protein than the body needs it simply gets stored as fat.

Moderate-protein diets, which are not as restrictive on carbohydrate consumption, are based on the more scientifically sound principle that proteins are satiating (fill you up for longer so you won't be hungry as often), which can result in a lower overall food intake.

New research from the University of Sydney compared four diets. Two diets were high-protein diets, one of which used high-GI carbohydrates and the other with low-GI carbohydrates.

The other two diets were high-carbohydrate diets, one of which used high-GI carbohydrates and the other used low-GI carbohydrates.

All of the diets showed significant weight loss since they were all low-energy diets but the least effective diet was the high-GI, high-carbohydrate.

The high-protein diets were effective for weight loss but the high-carbohydrate diet with low GI had the added benefit of lowering cholesterol levels and so lowering the risk of cardiovascular disease. Therefore for anyone concerned about their cholesterol levels, the high-protein diet may not be the best choice.

So the final word on very-high-protein diets is this: successful weight loss is not as simple as taking on the latest craze that 'really works' for some Hollywood star. It is a balance of long-term lifestyle changes: healthy eating habits that you can stick to; regular exercise that you enjoy; and using strategies to address the emotional and psychological factors that may undermine your good intentions.