The bewildering number of options we face when buying a single food product may turn out to be thwarting a natural body mechanism that regulates how much we eat.
Scientists have been studying our ability to judge, just by looking at a portion of food, how satisfying it is going to be. There is growing evidence that this so-called expected satiety wields a big influence on how much we eat. It directs what we choose to eat and the portion size we take, but also seems to influence how full we feel after a meal.
With experience, we build up a mental database of expected satiety which we deploy unconsciously before a meal. As part of the EU-funded Nudge-it project, a team led by Professor Jeff Brunstrom and Professor Peter Rogers from the University of Bristol in the UK wondered whether this natural accounting system is robust enough to guide us through the multiple versions of different foodstuffs available today.
The team studied pepperoni pizza, which they found is available in around 70 different varieties in the UK, ranging in calorie count from 500 to 1 900. Volunteers were quizzed about their pepperoni pizza habits and allocated either to a group that always ate the same brand or a group that switched between varieties.
When shown a slice of pizza, people who stuck to one brand expected that it would be far more filling than did people who ate a variety of brands.
The volunteers were allowed to help themselves to snacks and on one visit they were given a slice of pizza first. The brand-faithful group compensated for the slice by eating fewer snacks afterwards, while the other group compensated less and ended up eating far more.
The researchers think that the single-brand group were much better at controlling their food intake because they were less baffled by the complex food environment around them.
The idea fits with a growing body of research that, in the absence of confounding signals, our bodies are capable of keeping us slim.
‘We’re all incredibly good, actually, at keeping a stable weight, and it’s a very tiny drift that pushes us into obesity,’ said Professor Gareth Leng, an experimental physiologist at the University of Edinburgh in the UK, and coordinator of Nudge-it.
Part of that system consists of hormonal feedback loops triggered when the stomach fills. But expected satiety may turn out to be of profound importance.
Rats served food sweetened with low-calorie sweetener instead of sugar, eventually seem to equate sweetness with no energy. They will then happily overeat by gorging on other, sugary foods when normal rats would not.
Nudge-it scientists are now taking a look at how food is presented in canteens to see whether it is giving out deceptive messages.
‘We need to work with our physiology rather than against it,’ said Prof. Leng.
The ultimate goal of Nudge-it, which brings together a host of disciplines from brain scientists to behavioural economists to endocrinologists, is to find small but robust ways of intervening to set us on a healthier course of eating.
One team is testing the effects of giving a daily box of fruit and vegetables to 300 poor families in the UK. They want to see whether the intense exposure to new tastes and ways of cooking leads to any long-term change in behaviour.
‘There are obvious policy implications to do with supporting the availability of fresh food,' says Prof Leng, but he stresses that policy ideas need to be tested from all angles, to check for flaws and unintended consequences.
Elsewhere, insights into the eating habits of the poor children and their families in Portugal, the UK and Norway are coming from a project called Families and Food in Hard Times, headed by Dr Rebecca O’Connell at University College London, UK, and funded by the EU’s European Research Council.
Treating obesity-related diseases accounts for approximately 7 % of annual health spending in EU Member States.
With a 2015 report from Oxfam saying that the number of Europeans living with ‘severe material deprivation’ had risen to 50 million, the research team is unpicking exactly what that means for individual families existing in so-called food poverty and how it differs across Europe.
One consequence of struggling to feed a family, Dr O’Connell’s team have found, is that parents become conservative about their purchases, choosing items with a long shelf life, high energy content and guaranteed likeability — in part because financial constraints make avoiding waste a priority.
Thus, at a time when children are encouraged to experiment with tastes and could be setting up healthy habits, they are often confined to high-fat, high-sugar processed food.
Interviews with families have revealed coping strategies such as mothers locking the kitchen between meals, banning their children from inviting friends round so there are no extra mouths to feed, and going hungry themselves.
The team is also looking at families’ expenditure on food in comparison with a minimum standard for a diet that is not just healthy but also socially acceptable and allows a little socialising. ‘It was quite striking that in the UK there were particular family types spending much less — lone parent families and large families’ said Dr O’Connell. ‘And the proportion spending a lot less has gone up over time.’
On the positive side, the researchers have found some evidence that, in the UK, government interventions in schools, such as subsidised breakfast clubs and free fruit, are having an impact on the eating behaviours of less affluent children.
For those of us who feel we need help changing our eating behaviours outside the home, an app is on its way.
Researchers from the FoodSMART programme, funded with a Marie Skłodowska-Curie grant, are working with meal providers, especially in work canteens, to find a way of processing a mass of data about their dishes — not just their calorie counts but also their food miles, provenance and a host of nutritional information.
So when you are stumped about whether the mozzarella panini or the chicken korma better fits your needs, you will have the answer at the touch of a button, as the app will already know what’s important to you and will have data, courtesy of the food provider, that is specific to the dishes on offer.
Professor Heather Hartwell, a nutritionist who coordinates the programme from Bournemouth University, UK, said: ‘The moment you eat out you don’t have a clue about what you are eating.’
She envisages walking into the work canteen and seeing the top three most suitable dishes highlighted on your smartphone. As many people eat in such canteens daily, there could be a sustained effect on people’s diets, she believes.
The app will be tested in the first work canteen — the Institut Paul Bocuse, in France — this September.
How to harness your body’s natural weight control:
- Stick to the same brand or variety so your body learns how filling it is
- When you eat, just eat, don’t do something else at the same time so your brain realises what you are doing
- Eat slowly: people who take longer over their food eat less
- Tackle stress: high-fat, high-sugar food alleviates the body’s stress mechanisms and so it is harder to resist if you are feeling down or under pressure
- Avoid repeated dieting, it will upset your body’s natural feedback mechanisms