Pulp up the volume

THERE is, it seems, only one way to lose weight if you are a celebrity and that is to avoid food. Or at least to avoid chewing it. Dukan, Atkins and other diet fads that advocate the restriction of a food group come and go out of fashion, but the only steadfast route to super-skinniness appears to come in liquid form.

From the maple syrup diet, reportedly favoured by Beyoncé, which requires followers to subsist on daily drinks alone, and the cabbage soup diet to the ‘blend’ trend for consuming pureed baby food — Cheryl Cole is a fan — and the ‘broth’ diet followed by Angelina Jolie, it’s a case of not so much nil by mouth as swill (and then swallow) by mouth when it comes to achieving that A-lister body.

Not that all nutritionists see it that way. Many are scathing about diet plans that involve ditching solids, claiming we have a physiological need to chew food and that the act of masticating helps to release and assimilate molecules of nutrients from food. Their argument is that the longer a food remains in the mouth, as it does with solids, the more adept our tongues become at recognising its flavours, eventually sending messages to the brain to release the necessary digestive juices.

Chewing and digesting food fills you up. This whole process is disrupted when calories are consumed in liquid form instead. As juices and purees pass more quickly through the digestive system, the upshot is that you’re likely to feel hungry again more quickly. In terms of weight loss, it can prove a futile slog.

“Liquid diets such as the ‘baby food diet’ and the ‘cabbage soup diet’ will cause weight loss because they restrict the amount of calories consumed, but they also restrict important nutrients which is not good long-term,” says Helen Riley, a nutrition scientist. “Generally, it is very hard to stick to these diets and people don’t maintain the weight lost.”

But is the tide beginning to turn? A glut of studies have suggested that pulped and squeezed food may well have a greater role to play in aiding weight loss — and general health — than was previously thought. Last year the American Journal of Clinical Nutrition found dieters achieved better results when pureed vegetables were added to some of their favourite dishes.

Researchers at Penn State University gave 20 men and 21 women dishes such as casserole or macaroni cheese to which pureed cauliflower, butternut squash or carrots had been secretly added. While the subjects noted no changes in flavour, results showed they ate 200-350 fewer calories per meal when served the meals containing pureed vegetables.

“We had a huge effect on energy intake,” said Dr Barbara Rolls, director of the laboratory for human ingestive behaviour. “We’re adding cups of veggies to recipes and people don’t even notice.”

It was Dr Rolls who discovered in earlier research that people who consumed a bowl of soup before a main meal reduced their overall energy intake by 20%.

In one 2007 study, she and her colleagues looked at whether the degree to which a soup is blended affected satiety different ways. While ingredients remained the same — chicken stock, broccoli, potato, cauliflower, carrots and butter — the ‘form’ of the soups changed with those tested including ‘thin’ broth, chunky vegetable soup and a fully pureed variety. Results of her study showed that no matter how thoroughly it is blended, soup is filling and helps dieters eat less.

Other types of liquid calories don’t have the same effect. “Soup is filling because there is lots of volume but few calories,” Rolls says.

In June 2011 came evidence in favour of a more extreme liquid diet approach. Researchers at Newcastle University in Britain found that following a very low calorie (600 per day) liquid diet for eight weeks not only resulted in an average weight loss of 33 pounds but reversed Type 2 diabetes in people newly diagnosed with the disease. After just one week on the diet, which required subjects to consume only special liquid diet drinks and non-starchy vegetables, Professor Roy Taylor found that their pre-breakfast blood sugar levels had returned to normal. MRI scans showed that fat levels in the pancreas — “which inhibits the action of beta cells in making insulin” when too high— fell from a raised 8% to a normal 6%. By the end of the liquid diet, the diabetes was effectively reversed as their bodies were producing sufficient insulin. “What I can tell you is that if people lose substantial weight by normal means, they will lose their diabetes,” Taylor says.

What this swell of evidence means for the rest of us is that we now have the green light to drink or slurp more of our fruit and vegetables than before. Previously, the pulped drinks could count towards only one portion of the recommended five-a-day, but now, provided a smoothie contains at least 150ml of 100% fruit juice (no added sugar or dairy as in some commercial varieties) and 80g of pulped fruit or vegetables, it is said to count as two servings.

“In fact, it is possible to take all your five-a-day in pureed form,” says dietitian Eileen Steinbock. “But the important thing is variety — all five should be different.”

Steinbock says vegetables are often a better choice as a smoothie ingredient. When a fruit and vegetable is crushed or pulped the natural sugars it contains take on a different form. “The cell walls hold natural sugars inside a fruit or vegetable but when they are broken through blending or cooking these so-called ‘intrinsic’ sugars are freed from their structure,” she says. “It is when they become ‘extrinsic’ in this way that sugars are more damaging to teeth. Vegetables are better as they generally have less sugar.”

Despite having more sugar, a cocktail of fruits can hold enormous health benefits. A team from the University of Strasbourg put 13 exotic fruits into a blender to create a ‘super-smoothie’ that was shown in tests to relax the heart artery walls of pigs that consumed it and, suggested the researchers, would likely boost blood flow to the heart in humans.

Their findings, published in the Royal Society of Chemistry’s journal Food and Function, also showed that the drink’s antioxidant content helped to mop up free radicals that can damage DNA and cells. Hardly surprising that the formula has since become a hit among those looking to defy the ageing process, such as Simon Cowell, 53, who reportedly drinks the formula every day. With each glass containing 30 grapes, 15 blueberries, 9 strawberries, half an apple and more, it would be difficult to munch through that amount in one sitting. Yet there is more to it than the nutrient content. Sip a smoothie and you feel virtuous, internally cleansed, somewhat superior to your coffee-slugging counterparts. Have one for breakfast and your dieting psyche is set so that you are less inclined to sinfully indulge before lunchtime. Even if they don’t aid weight loss or fail to add years to your life, smoothies leave you nutritionally smug. And there’s no better feeling than that.