Air and water crucial in fight against obesity

Air and water are substantially neglected - and cost effective - weapons in the battle against the bulge, according to scientists gathered at a major London conference on satiety last week.

Studies unveiled at the conference - organised by The British Nutrition Foundation - repeatedly demonstrated that food energy density, structure, volume and macronutrient composition (eg. fat, carbs, proteins) were vital in determining how filling it was.
Thus two meals with the same amount of calories and macronutrient content could have different effects on satiety and subsequent food intake at later meals if one was significantly heavier than the other owing to additional water content. That was the verdict of Dr Barbara Rolls from Penn State University.
Dieters could eat more food and still lose weight by focusing on products with a lower energy density (calories per gram), she said. However, water needed to be incorporated into the structure of the food rather than drunk as an accompaniment. A good example of this was a casserole eaten alone, eaten with a glass of water, or eaten as a soup (by adding the glass of water to the casserole and putting it in a blender).
Each contained the same number of calories, but the soup was the most satiating and reduced subsequent food intake at later meals more than the other meal options.
Air was also much neglected in satiety studies, she added, citing the example of cheesy wotsits, which were more satiating the bigger (more puffed) they were. Here, a combination of cognitive, sensory and physiological factors was probably at play, she said.
Professor Rob Welch from the University of Ulster added: “Gas in foods is a relatively neglected component that can impact on satiety.” Studies had shown that increased aeration - in whipped confectionery products, ready to eat cereals and even carbonated soft drinks - increased satiety and reduced food intake at subsequent meals, he said.
Food structure was also recognised as an important factor in satiety, added Welch, with whole apples proving more satiating than an equivalent quantity of apple in puree or juice form, for example.
The spanner in the works, according to psychologists at the conference however, was hedonics - or the issue of food preference and palatability. Frustratingly, said professor Martin Yeomans from the University of Sussex, even if you are completely sated by your high volume, low energy dense meal, you can still find room for dessert.
In one study, students were given a high energy breakfast and then invited to an ‘all you can eat pasta meal’ for lunch, he said. The breakfast was very filling, so none of the students were particularly hungry at lunchtime. Those given a bland pasta dish ate a relatively small amount at lunch. Those given a tastier, more palatable, pasta dish that was exactly the same but with more herbs ate considerably more. “When you are sated [full], you’re much more prone to palatability effects,” said Yeomans.