Feeling ‘full’ on less food

This post originally appeared on FutureFood 2050, a new publishing initiative from the Institute of Food Technologists that investigates how we will feed over 9 billion people by the year 2050.

Julian Mercer, a leading UK obesity researcher, heads a European team exploring how to create healthy foods that are more filling.

Imagine tucking into a small bowl of breakfast cereal and feeling full until lunch, then eating a light sandwich that keeps the hunger pangs at bay until supper time. It may sound like the ultimate fantasy for dieters, but a team of food scientists believes the creation of new filling foods like these could help reduce growing obesity rates.

Julian Mercer

Julian Mercer


What we are actually doing in several different projects is trying to look at how hunger and satiety are regulated, and whether there are ways we can support people to consume a little bit less food.”
—Julian Mercer




Fat-fighting tactics that work from the inside out by appeasing appetites could be the wave of the future, says Julian Mercer, a leading UK obesity researcher and head of the European Full4Health project, a European Union-funded program exploring the body’s mechanisms of hunger and satiety (feeling “full”) to help combat obesity.

“Obviously we could just have a mantra of ‘eat less and exercise more,’ but it’s quite difficult for people to regulate that just through a conscious process,” says Mercer. “What we are actually doing in several different projects is trying to look at how hunger and satiety are regulated, and whether there are ways we can support people to consume a little bit less food.”

The food-gut-brain axis

Based at the Rowett Institute of Nutrition and Health at the University of Aberdeen, Scotland, Mercer and the Full4Health team are probing the food-gut-brain axis—the body’s internal signaling mechanism that helps determine whether we feel full, hungry or just plain gluttonous.

These sensations are complex and linked only partly to the physical sensation of food in our stomachs. The presence of food in the gut also triggers the release of an array of hormones, most of which signal to the brain when it’s time to stop eating, what types of food are being consumed and how they should be processed in the gut. One gut hormone is the odd man out, signaling hunger to the brain.

“Combined, this information contributes to decision making on how much you eat in terms of calories and what sorts of foods you might look out for over the next period of time,” says Mercer, who came into food research through the back door 25 years ago as an endocrinologist. “What we are looking at is how this food-gut-brain axis functions, and how manipulating the diet influences its function.”

In addition to getting gut signals, the brain is constantly receiving information about how much fat our bodies are storing from a hormone called leptin. This information helps us maintain a relatively constant body weight in the long term. If levels of leptin fall, due to dieting or starving, the brain responds by increasing appetite—one reason it is so difficult for overweight people to fight the flab.

Our brains also respond to food—particularly sugary and fatty food—with the release of “reward” and “pleasure” neurotransmitters. The surge in these chemicals can override our feelings of fullness, allowing us to indulge in sweet, fatty desserts despite already being full from dinner.

Protein power

Full4Health, which was launched in February 2011 with $11.3 million of funding, is focusing on animal research into the biological mechanisms that underpin satiety and hunger. The project is also looking at how the psychological and physiological reaction to food changes as we age by analyzing the brain response to food in children, adolescents, the middle-aged and elderly using functional MRI (magnetic resonance imaging) scanning.

While the human studies are ongoing, the animal research has already identified new roles and functions for gut hormones. The work is also adding weight to the “protein leverage hypothesis,” says Mercer—the idea that eating behavior is driven by the need to consume protein. Evidence for this idea has come from a Full4Health team led by Margriet Westerterp-Plantenga at Maastricht University in the Netherlands. Researchers there found that volunteers consuming a high-protein diet ate less than those on normal or low-protein diets but did not report feeling hungrier, although the reasons for this effect are still unclear.

Armed with the research results, Mercer’s team helped the UK retail chain Marks & Spencer develop a brand of high-protein ready meals called Simply Fuller Longer. The foods typically contain 10 grams of protein per 100 grams, about 5 grams more than comparable ready meals. In a study of the diet at Rowett, volunteers who ate the Simply Fuller Longer meals for four weeks saw an average weight loss of 5 percent, and researchers found that the high-protein meals delayed the onset of hunger by one to two hours.

Manipulating fiber for fullness

Mercer is also a partner in Satiety Innovation (SATIN), a European project concentrating on manipulating fiber to make it even more filling. Fiber stays in the stomach longer than other foods do, increasing the feeling of satiety compared with other foods. And as fiber goes down the gut, it is fermented by gut bacteria that release short-chain fatty acids, which are also satiating.

The SATIN team is looking at fermenting or heat treating fiber to see if the natural properties of fiber from fruit, vegetables and grains can be enhanced and then used as food additives, says Mercer. Jason Halford, who heads the SATIN collaboration of academics and industry at Liverpool University in England, demonstrated in August 2014 that consuming such a modified fiber—a proprietary whole-grain flour treated with a heat-moisture process—can increase the length of time a person feels full. When volunteers had a 20-gram breakfast serving of the product in a smoothie, they consumed 5 percent less food at lunch and dinner. SATIN research is also looking into the effects of arabinoxylan and beta-glucan, soluble fibers found in grains.

“An obvious fiber you eat in the morning is breakfast cereal, and that’s a place you could directly incorporate [enhanced fiber], but you could potentially incorporate it into bread and other normal things you eat,” says Mercer. “Ready [to eat] meals would be another obvious choice.”

Less is more

Research on filling foods is unlikely to move beyond protein and fiber, says Mercer, because other micronutients such as fats have far less potential. But one new line of satiety research that he believes has promise involves mimicking the effects of weight-loss surgery. Tests on rats by Full4Health researchers at Norwegian University of Science and Technology have shown that injecting the anti-wrinkle treatment Botox into the vagus nerve in the stomach leads to weight loss. The jab paralyzes the nerve, which plays a key role in feelings of hunger and controls the passing of food through the intestines.

Mercer says it’s too soon to predict how important the satiety approach to weight loss could become, “since we are still at the proof-of-concept stage in terms of whether satiating foods can deliver long-term health benefit,” he says. He adds that “it is unlikely that [the effect] would be big enough to help individuals who already have a significant weight problem, but more realistic to think that the approach might be helpful for people who want to maintain their body weight within the normal/overweight range and counter progression towards a more problematic weight.”

And he stresses that any kind of food product designed for greater satiety will also need to be palatable to consumers. “It has got to be something that is recognizable and something that tastes OK,” he says. “Ultimately you can easily invent diets that will help people maintain their weight, but if [the diets] are unpalatable they will be a failure.”

David Derbyshire is a freelance environment and science writer based in Winchester, United Kingdom. He is a former environment editor of the Daily Mail, and his freelance work has been published in The Guardian, The Times, and other newspapers.


Science Meets Food

The IFT Student Association (IFTSA) is a forward-looking, student-governed community of IFT members. Through competitions, scholarships, networking, and leadership opportunities, you’ll set yourself apart from your classmates (unless they’re members too).


  1. How does this differ from low GI foods? (I am not an expert but I was under the impression that these breads and cereals allowed you to feel fuller for longer because of the fiber content)

  2. If consuming a diet high in protein would result in a smaller amount being eaten , does the same effect occur when eating fat? if so, is this why the Banting diet is so successful?.

    • Hi Sue Ann
      I think it depends on what kind of fats you are eating, The Banting diet is successful because it uses a combination of high fat and protein and low carbohydrates. You can eat fat in relatively unlimited amounts, but only moderate protein. A healthy high-protein diet for humans doesn’t exist. If your diet was 100% protein, you’d quickly get sick and die. You can’t really overdose on fat, it reduces appetite, and it’s the best way to get over sugar addiction.

  3. According to Judy Caplan when you consume less carories you ultimately lose weight. So limiting portion sizes is a way of doing this, but it also can depend on what the portion of food is made up of. Slow transitions to reduce portion size will allow the body to adjust. Fat has a higher calorie count so initially people cut it out because it isn’t good for your health in large portions and it makes you lose weight quicker.

  4. Feeling “full” on less food is a great concept in an ideal world, but how do you plan on maintaining the nutritional content on the food? Will it not be sacrificed for the sake of “palatability”. After all this is ment to be a healthier way of maintaining weight and therefor it must be well rounded rather than just a mixture of undigestable fiber with traces of protein and flavourant in it.

    • Your point is extremely relevant. Although this diet says ” fuller for longer” are the meals actually including all foods groups and do they include all essential nutrients and minerals? As these need to be included in a well balanced healthy diet. Most importantly is this diet maintainable? Most diets these days give results over short periods of time however they cannot be maintained and the weight lost is put straight back on. Therefore are people able to lose weight and keep it off? U15001572

  5. eating less and still feeling full is everyone’s hope when taking part in any diet , but if we are to eat a high intact of protein as it helps as to feed full does this not have an affect on our bodies in the long run .As well as how can injecting our stomach with Botox be a solution to me it sounds very harmful in the end as it is not natural to do that . And a key thing that is left out in all of the above it that a key concept to maintain an ideal weight is through exercise.

  6. Eating only three meals a day would be very convenient, concerning people who are especially dieting. Is it not healthier though to eat more often in little portions so that the metabolism keeps on working? In the same breath i am asking whether or not this will not slow down the metabolism? I absolutely love the idea of eating only three times a day, it would surely save a lot of time, but is it healthy in the long term?


  7. What is with the proliferation of 8-digit numbers having conversations on this site?

Leave a Reply