Like most approaches to battling the bulge, appetite regulation becomes depressingly complex the more you delve into it. Consider this: is whey protein more filling than casein? It depends. If you gave volunteers an all-you-can-eat pizza meal 90 minutes after they had drunk a protein drink, whey would have dented their appetite more than casein. Repeat the experiment but wait 150 minutes till you serve up the pizza buffet and the result would be reversed. So which is better?
The basic design of a satiety study is not in itself very complicated: you give volunteers a 'pre-load' of your test food or a control food; you ask them at regular intervals how hungry they feel using VAS (visual analogue scale) scores; and you invite them to a buffet a couple of hours later and measure how much they eat. Separately, hormones associated with appetite regulation such as ghrelin, GLP-1, CCK and PYY can also be monitored via blood tests.
So far, so good. But the problems are all in the protocols. What is the control food? Do the volunteers like what you're serving up in the buffet? Do the VAS scores correlate with the results of the hormone tests and the food intake study?
The devil is always in the detail, says Unilever senior scientist Dr David Mela, who has built up an international reputation for his work on satiety. "Controls are inappropriate, data is taken out of context or the product tested is not representative of the end product, either in terms of dose, or the food matrix. Likewise, there is often no evidence that manufacturers have proved their product still works after processing and storage."
Yet the commercial pressure to make a fast buck out of the obesity crisis has nevertheless spawned a whole swathe of hunger-busting ingredients, many of which are not supported by "anything even approximating sound science", claims Mela.
There is also the question of degree, notes John Blundell, professor of biopsychology at the University of Leeds. After all, everything you eat, from chips to doughnuts, will trigger physiological responses including filling your stomach and triggering the release of certain gut hormones, but this doesn't automatically make chips a great 'satiety' food, says Blundell. "Appetite isn't rocket science. It's far more complicated than that!"
At the very least, he says, manufacturers must consider what they are trying to achieve. Is appetite suppression a useful endpoint in itself? If you have a clinical study that proves that product X keeps you 'fuller for longer', but does not ultimately help you consume fewer calories, what is the point of it? Conversely, if product Y has a big effect on CCK, and makes people eat less at subsequent meals, but does not make them feel noticeably fuller, will they buy it again?
They also need to consider how important appetite actually is in weight management, says Blundell. After all, hunger is self-evidently not the only factor governing how much we eat, what we eat, or when we eat. If only it were that simple.
The problem, says Blundell, is that growing numbers of us now live in an environment that makes it too easy to over-consume. "Our natural satiety mechanisms are not strong enough to combat the obesogenic environment we're living in."
Palatability therefore presents "something of a conundrum" to the food developer, he says: "You want your product to look and taste good, but the more appetising food is, the more prone consumers are to ignoring what their bodies are telling them."
But pushing these difficulties aside, what is actually in the toolkit for the product developer looking to develop more satiating, but less energy-dense products?
At the moment, the most popular options are fibres (oligofructose, inulin, guar gum, polydextrose, corn), proteins (soy, whey, milk, pea, potato), and combinations of the two - as used in Kellogg's Special K Sustain cereal or Danone's Shape 'Feel Fuller for Longer' yoghurts, says Kavan Ranasinghe at DKSH. "Many big brands are pretty conservative. They want something that sounds recognisable and won't have a negative impact on taste and texture. Fibres and proteins meet this criteria, along with beta-glucans, which can boost satiety and are low-GI (glycaemic index)."
While green tea attracts a lot of column inches, many manufacturers are "reluctant to use it in weight management products as they feel it hasn't been proven", he says. "The same probably applies to creatine and carnitine, which have done well in the sports nutrition market, but have not really hit the mainstream."
There is also the issue of cost: "If you are taking a staple like a breakfast cereal or a yoghurt and adding proteins and fibres, it costs a bit more, but it's something that consumers already buy. If you are producing a functional food that they wouldn't normally buy and charging £2.99 (euro 3.74) for four mini-drinks, that's much more of a gamble."
Despite all the hype, he adds, "a lot of the satiety ingredients have actually been around for ages, they just get a new spin every couple of years - from sugar or fat replacement to low-GI, and now satiety."
That said, spinning something in a different way can help consumers think about food intake more carefully, says nutritionist Azmina Govindji, who has helped advise Danone on weight management. "If something says this will make you feel fuller for longer, it does make you listen to the signals your body is sending out more carefully."
From a marketing perspective, big brands are also trying to move away from negative to positive messaging, says Kellogg senior nutritionist Rimi Obra-Ratwatte. "Special K is not about dieting and denial, but about hunger management. We are trying to be an ally, helping customers in their everyday struggle. But you have to choose the right ingredients and the right vehicle."
Whether eating a few extra yoghurts with added guar gum and milk proteins is really going to encourage more fundamental diet and lifestyle changes is of course highly questionable, observes professor Peter Rogers, a psychologist at Bristol University. "The satiety approach should apply to your overall diet - to aim to eat more satiating, but less energy-dense foods across the board. It has to be a wholesale approach."
Indeed, if they really are going to help consumers, food developers need to think about the following questions whatever they are formulating, says Danisco Sweeteners scientific affairs director Julian Stowell: "How many calories does this contain per gram? How much fibre is in it? What is the glycaemic response?"
Jordans Cereals taste and development manager Kirsten Hoskisson adds: "We think about glycaemic response and how satiating something is for all of our products and we spend a lot of time playing around with nuts and cereals with different protein and fibre content. But the challenge is communication. I'm not sure consumers really get GR or GI. We're also not keen on adding 'functional' ingredients people haven't heard of or wouldn't expect to find in a breakfast cereal or bar."
As for weight management ingredients used in supplements, not all of them translate well to mass market food products, predicts Joy Thomas, business manager at ingredients distributor Cornelius. "Some ingredients have got a bad name because they have unpleasant side-effects. Others may work in foods but sound too scientific. However, some satiety ingredients could translate well, especially if they are seen as 'natural'."
One such is potato protein, which Cornelius distributes in the UK for Kemin Health under the Slendesta brand. This is easy to incorporate into foods and could work in a variety of products from smoothies to cereal bars, says Thomas.
As for marketing, scores of applications to make health claims about weight management ingredients from yerba mate to bitter orange, chitosan, green tea, calcium and green oats have been submitted to the European Food Safety Authority (EFSA) for assessment under the EU Nutrition and Health Claims Regulation along with several generic claims linking fruits, nuts, wholegrain foods, proteins and fibres to weight control.
At this stage, it is too early to predict how many will gain approval, although experts predict many applicants may get a nasty shock when the list of approved claims under article 13.1 of the Regulation is published in January 2010.
So how high are the stakes? For some hunger-busting ingredients such as oligofructose and inulin, corn fibres, polydextrose and gum arabic blends, rejection by EFSA would not be the end of the world as satiety is just another string to an already full bow (high fibre, low GI, prebiotic effects, fat and sugar replacement).
By contrast, an approved health claim is arguably mission critical for the two highest-profile branded ingredients in this market: PinnoThin (Korean pine nut oil) and Fabuless (a palm and oat oil emulsion), which do not perform any other useful function in a food, so must stand or fall on their health claims.
The ultimate test, of course, is not whether this new breed of hunger busters can impress regulators, but whether consumers actually want to buy them, and here the evidence is quite hard to come by.
A quick scan of Mintel's global new products database reveals several products marketed on a satiety platform from small and large brands, including Tracy Stern Salon Tea in France (with green tea, yerba mate and other natural extracts "said to have the natural power to decrease appetite and speed up the metabolism"); Danone Shape Feel Fuller for Longer yoghurts (with a "hunger control formula of fibres, protein and a creamy texture"); Kellogg's Special K Sustain cereal (with soy protein, soy nuts and wheat fibre to "help keep you satisfied for longer") and Naturally Gorgeous juice drinks and chocolate (with PinnoThin Korean pine nut oil to "help you feel fuller for longer") in the UK.
Some, such as Sacia Slim appetite suppressant chewing gum in Spain, are more wacky ("now with garcinia cambogia and karaya, two natural ingredients known for their strong filling effect").
Others such as Nestlé Sveltesse yoghurts (with proteins and inulin "to curb appetite and provide a full feeling") are more mainstream. Most manufacturers in this market will not divulge sales figures, although Unilever insists sales of its Hunger Shots (with whey protein and soluble fibres) have been "encouraging, with strong levels of new consumers entering the mini-drinks category as a result of the [recent UK] launch". The only concrete figures relate to Campina's Optimel [and Optiwell] Control drinks in Germany and the Netherlands, which contain Fabuless. And they're good.
Whether rivals have built enough momentum to keep their coveted supermarket listings, only time will tell. One thing is for certain, none of us is getting any thinner, so anything that can truly help us keep the hunger pangs at bay has to have a sporting chance.
Body shaping: lose fat the natural way?
Appetite regulation is, of course, only one approach to weight management. Others focus more on body shaping via fat reduction.
The best-known ingredient for fat loss is probably conjugated linoleic acid (CLA), which is claimed to influence enzymes involved in fat metabolism and activate receptors associated with fat storage, helping people to decrease the amount of fat stored and utilise more fat as energy.
While CLA has had some success in supplements, its expansion into the EU food and drink market has however been thwarted by regulators, who have insisted that CLA from safflowers is subject to the Novel Food Regulation, despite the fact that it is a naturally occurring fatty acid found in beef and milk that has been eaten in Europe for thousands of years.
After a long wait, however, applications from the two firms driving this market (Cognis with Tonalin CLA and Lipid Nutrition with Clarinol CLA) are both likely to be approved next year.
Meanwhile, both firms are confident that a health claim about CLA and body shaping, which is supported by some serious scientific evidence - comprising studies on the ingredient alone and in food applications, will be approved under the Nutrition and Health Claims Regulation in 2010.
But what do food manufacturers make of CLA? From a technical point of view, it is pretty flexible, says Lipid Nutrition global marketing manager John Kurstjens. "We can supply it in oil and water-dispersible powder forms, enabling it to be used in a wide variety of applications from milk drinks, fruit juices, yoghurts and yoghurt drinks to baked goods, salad dressings and breakfast cereals."
The biggest challenge, he accepts, is communication: "CLA isn't recognised as a food ingredient, so just adding 'with CLA' is not enough."
But Cognis product line manager for Tonalin CLA, Arne Ptock is convinced branding will overcome potential problems: "This isn't about complicated chemicals, but incorporating a consumer-friendly brand into a product that comes with a powerful message: reduce your body fat. It's not actually about weight loss."
The recommended dose is 1.5-3g/day, which could be spread across one or two servings, says Ptock. "In markets where we have foods with CLA, we've seen manufacturers with a mark up of 100% over a equivalent product achieve good rates of sale. For example there are fermented milk products in Saudi Arabia and drinkable yoghurts in Peru."
Now that CLA has GRAS (generally recognised as safe) status in the US, manufacturers across the pond are also experimenting with different food applications, he adds: "Dairy and beverages seem to be the most popular areas of experimentation at the moment."
But there is competition in the body shaping stakes, notably from Prolibra, a whey-derived milk mineral complex from Irish dairy giant Glanbia. This is claimed to promote fat loss and help retain lean muscle mass. It also benefits from having a consumer-friendly ingredients declaration and broad functionality, says Alma Mullins, who works in Glanbia's innovation centre in Kilkenny. "We're talking to companies in supplements, bars, bakery, dairy and beverages."
Weight management toolkit
* SATIETY: Dietary fibres (corn fibre, acacia gum, guar gum, inulin, oligofructose, wheat fibre etc), proteins (soy, whey, casein, pea, potato); Caralluma fimbriata; Hoodia Gordonii; Yerba mate; pine nut oil; palm and oat oil emulsions; alpha-lipoic acid; nuts; resistant starch; HCA (hydroxycitrate from purple tamarind fruit): hydrolysed collagen; white beans
* THERMOGENESIS AND FAT BURNING: Capsaicin, green tea, CoQ10, brown seaweed extracts, various spices
* BODY SHAPING: Caralluma fimbriata, CLA, milk and whey proteins, green coffee beans extracts, seaweed extracts