Science Interviews

Interview

Sat, 8th Sep 2012

Can we change our diets to help us lose weight?

Alexandra Johnstone, Aberdeen University

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Ben -   Researchers in Aberdeen are now trying to develop new types of diet food that help you cut calories by making you feel fuller for longer.  Dr.  Alexandra JohnstoneÖ

CakesAlexandra -   Well, I'm interested in appetite control and that mostly is applied within the context of weight loss because one of the main reasons why we fail to lose weight is because we feel hungry.  So, if we can develop dietary strategies that help control appetite then weíll help people lose weight.

Ben -   So, regardless of the content of the diet itself, the problem is that we keep eating and we eat more than we should.

Alexandra -   Yes, we have a huge obesity epidemic in the UK and it will be nice to think if we would have preventative strategies to stop our waistlines expanding further, but we also need therapy.  So, itís not just drug therapy.  Itís not just bariatric surgery.  We need other lifestyle approaches to help people maintain and manage their body weight.

Ben -   So, what is it that stops our appetite?  How do we actually feel full?  Is it more than just literally filling up the bag that is our stomach?

Alexandra -   Well, the volume of the food of course is important and thatís governed from the stomach, but the work that I'm interested in is the role of protein in influencing how full we feel.  Thatís when I use the word Ďsatietyí.  So, what I'm interested in is protein induced satiety, so what is it about protein, the macro-nutrient protein that helps fill us up and makes us feel fuller for an extended period of time?  Just to remind you, our protein sources are primarily from meat, whether red meat or fish, poultry, but can also be non-meat sources from cereals, dairy products, and peas, beans, and pulses.

Ben -   Protein of course is a huge over action termed for anything thatís made up a long chain of amino acids.  So, it really could be any source of protein or are we looking at specific proteins that we think have an effect?

Alexandra -   The work that I've done would tend to indicate that vegetable and meat source protein are both effective at influencing appetite during weigh loss.  So thatís encouraging.  So, it gives us insight to a variety of different sources that we can use to try influence how full we feel.

Ben -   So, what do we think is actually happening when we eat protein compared to letís say, a high-fat diet or a high-carbohydrate diet?

Alexandra -   Thatís a good question.  I'm not sure I have the answer unfortunately, but some of the mechanisms that will be involved is when protein reaches the stomach and then is digested and partly absorbed, then that will influence the gut hormones that are released from the stomach and they are fed directly into the brain via the vagus nerve.  So, we know that thatís potentially one of the mechanisms.  Other mechanisms, as you said is the amino acid structure of the proteins and that the change and influx of amino acid concentration in the blood would potentially also influence the brain.  I keep mentioning the brain because itís our traditional view that the brain is very important in regulating and sensing changes in energy, and is thought to be our traditional hunger and fullness centre.

Ben -   So, what are we going to do now to investigate this further, if we still need to shed some light on the physiological mechanism?  What can we start doing?

Alexandra -   Today, weíve been speaking about a work thatís funded by the EU.  Itís a very large multi-million project across 9 European countries and 18 academic and food industry partners.  So, itís pulling together all that expertise to develop new products that can be tried and tested in humans to help control appetite.  And skipping forward a few years, within the SATIN grant, or satiety innovation is the name of the grant, weíll be looking at how diet can influence appetite with a view to helping people lose weight.

Ben -   So, lots of research is done telling us what foods we should and shouldnít eat, and the right sort of balance, and how much red meat weíre supposed to eat per day, and so on.  You're taking that a step further in looking at developing new foods that have the right protein mix or the right components to actually make us feel fuller.

Alexandra -   Thatís exactly right, yes.  We will be testing it in a whole diet, itís going to be done in Denmark, so we have volunteers where they're provided all of their food items for an extended period of time - say, 6 months.  So, weíll be able to look at changes in body weight over that prolonged period of time.  So itís quite a challenging project.

Ben -   The other way to look at this though is that problem is responsible for telling people that they're full, and we know some people in conditions where they might be ill, need to actually eat more and they need to overcome their own feeling of fullness in order to take on more calories.  Can we do essentially the reverse of what weíre talking about and engineer foods so that people can take more on before they feel satisfied?

Alexandra -   Yeah, thatís a very good point to make in that although weíre dealing with the obesity epidemic, there is a small proportion in the UK, nonetheless, extremely important and thatís the elderly undernourished.  Protein probably does have a role to play and certainly, some of my work involved in other EU funded projects, looking at the role of protein in a liquid form and how that influences appetite and food intake.  So, in that sense, itís used as a between meal kind of supplement in order to give them essential nutrients and vitamins, and minerals in a drink form that can help potentially improve quality of life.

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