Dr. Sean Wheatley, PhD – Researcher and Trainer in Public Health
Why is this topic important?
For many people managing health and weight is a priority, but it can also be a struggle. Understanding what causes hunger is key, because it is all but impossible to manage these things if you do not get hunger under control first.
This week’s blog looks into the possible key, but often overlooked, impact of nutrient intake on hunger. But first, a quick summary of some of the other main reasons we feel hungry.
It’s all in your head?
The main purposes of eating are to make sure we have enough energy and to provide our body with the building blocks to fulfil other vital functions. But for many people hunger is often not driven by these physical needs, but rather it is caused by psychological factors such as boredom, habit, stress or emotions.
These psychological drivers of hunger can be a key factor in causing people to overeat, in part as there is often no threshold at which the body (or mind) shuts them off. This means people can eat more and more and more without ever feeling full! Compounding the negative effects of this, the foods we reach for in these situations are rarely good for us...
In order to manage your hunger it is important to be able to identify if/when you are eating for psychological reasons; and to find strategies to deal with this. A recent blog we wrote provides some practical hints that can help you with this.
Once the psychological drivers of hunger are under control you can start to consider the physiological reasons. This can help you make better food choices, leading to reduced hunger and making the management of health and weight easier.
Meeting your body’s needs
Physiological hunger is when your body is trying to get you to eat because of an actual, physical need for food – or at least because it thinks there is a need for it. This can be due to:
- a genuine lack of available energy (i.e. we are truly starving)
- the body not being able to use the energy it does have stored properly, causing the body to think there isn’t enough energy available
This latter case is more common in the UK (and much of the developed world) as most people have more than enough energy stored in their body. High insulin levels (hyperinsulinaemia) and insulin not working properly (insulin resistance) are commonly implicated in this inability to access stored energy, because:
- when insulin levels are high the body will be in fat storage mode, so any fat the individual has stored on their body (or any fat that is in the food we eat) cannot be efficiently used for energy
- if insulin is not working properly the body will struggle to move glucose from the blood into the cells to be used for energy, so this glucose and the body’s glycogen (carb stores in the body that break down into glucose when needed) cannot be efficiently used for energy either
Not all foods are created equal
If hunger was only linked to energy requirements all foods would have the same impact on how full we feel, as long as we ate the same number of calories from the different foods. But we know that this isn’t the case!
There are many properties of foods that impact how they affect satiety (fullness) levels, including:
- how quickly the body can break them down and absorb them; for example high fibre foods can help us feel full because they take a long time to digest
- the volume of the food; foods that take up a lot of space will make us feel full (at least until they’re digested) because the body needs to create space before more food can enter the digestive system. Gastric bands and other weight loss procedures work on this same principle: if there is no/less room for food, hunger is suppressed
- the food’s influence on certain hormones, including those which make us feel full and those which affect how nutrients are used or stored
These factors are mostly well known, but what is often overlooked is that the type(s) and amount of nutrients a food provides, as well as its nutrient density, might have an important effect too.
What is nutrient density?
A nutrient is something that provides nourishment to the body. It can be used for growth and/or other important functions. The nutrient density of food refers to how many nutrients can be found in any given amount of a food.
A nutritionally dense food provides a lot of nutrients in a serving, whilst a food with poor nutritional density would have fewer beneficial nutrients in a serving of the same size.
As well as a need for energy the body also has a need for some of these nutrients. It is therefore logical that we would have evolved a way to try and make sure we have a high enough intake of the most important ones, to reduce the risk of deficiencies which can be detrimental to our health.
Just the essentials
Any nutrient that our body cannot make itself is classified as “essential”. We need to consume enough of these essential nutrients to meet our body’s needs, and prevent potentially dangerous deficiencies.
Many of these nutrients cannot be stored in the body either, so we need to consume them regularly in order to keep meeting these requirements.
Essential nutrients include:
- Some amino acids, which are found in protein
- Some fatty acids, which are what fats are made up of
- Some micronutrients, in the form of vitamins (like vitamin C) and minerals (such as iron and calcium)
The importance of proteins
Proteins, or more correctly some of the amino acids that proteins are made up of, are essential. They are needed for growth and repair, and we cannot store an excess of them for use later on. That means we need to have a source of protein in our diet on a regular basis.
The protein leverage hypothesis suggests that this need for protein is the main driver of hunger.
If we eat foods that have a high protein content then we will reach this protein requirement quickly, and so we will feel less hungry and, as a result, eat less. On the other hand, if we eat foods that don’t have much protein then we will need to eat a lot of them before we meet our body’s needs for protein. This means, based on the protein leverage hypothesis, we would need to consume a LOT of food before we stop feeling hungry.
The more food we eat before we meet this protein requirement, the more likely we will end up consuming more energy than our body needs; with any excess being stored as glycogen or fat, resulting in weight management problems.
Beyond protein: the nutrient leverage hypothesis
Okay, I might have made this name up (I might not have, but a very quick Google search didn’t show anything up); but the principles underlying it (which I definitely can’t take credit for) are essentially the same as those of the protein leverage hypothesis so I think this name makes sense. With the protein leverage hypothesis it is just a certain amount of protein we need to consume before our body reduces hunger, but with the “nutrient leverage hypothesis” our need for certain other essential nutrients needs to be met too before the urge to seek out more food is stopped.
This would be a useful system as it would minimise our risk of not consuming enough of any of the essential nutrients, minimising the risk of the potentially catastrophic consequences of being deficient in any of them (think scurvy without enough vitamin C or rickets with insufficient vitamin D).
Real world impact
Our biggest problem in relation to this need for nutrients, and the impact this has on hunger if there is any truth to this hypothesis, is that the food market has been flooded by low quality products with poor nutrient density (i.e. for any given amount of these foods there aren’t many of the essential nutrients we need). Many convenience foods are high in refined flour, processed vegetables oils and/or sugar; ingredients that do not contribute much to our body’s nutritional needs. As a result we have to consume a lot of these foods before we cross the threshold at which our body has had enough of the essential nutrients, and until we cross this threshold we will to continue to feel hungry.
In contrast, the foods that are best at keeping us feel fuller for longer tend to be higher in protein and/or fibre. Now it is entirely possible that this is due to effects that are specific to the protein and/or fibre in these foods, but these foods also tend to be more nutritionally dense in general (i.e. they often include a variety of other vitamin and minerals). It is therefore possible that at least part of their satiating effect is due to the delivery of nutrients beyond just the protein or fibre they contain.
So how much of each nutrient do we actually need?
Good question; but this is difficult to answer, particularly in what is (supposed to be) a short blog. The government’s targets for nutrients are either based on evidence from people with deficiencies, giving an indication of what the thresholds are to stop people experiencing unwanted side effects, or based on averages in healthy populations, estimating what is “normal”.
But different people have different needs for different nutrients (what does “normal” even mean?!). So whilst these recommendations can provide a guide, that doesn’t necessarily mean these targets are the same as what is optimal for YOU.
This question is also complicated by the fact it is difficult to know exactly how much of some of these nutrients will be in the food you are eating, and it is almost impossible to estimate how much of these nutrients you will actually absorb from your food because this, again, is very different for different foods and for different people.
Should I track my nutrient intake?
It isn’t usually necessary to do this, but if you like to track things this might be something you find helpful and/or interesting. There are a number of different apps and resources that can help you do this. There is a danger though of becoming obsessed with targets (targets that, as explained above, might not even be right for you) if you try and track your intake of every nutrient that you need.
A sensible approach for many people, whatever dietary approach they are following, is simply to try and have a varied diet that includes lots of nutritionally dense, minimally processed foods. This will likely help you meet most of your dietary needs and therefore, based on the ‘nutrient leverage hypothesis’, reduce your hunger levels.
If you do have any concerns about whether you are having enough of certain nutrients you may wish to experiment with tracking your food intake, or you could seek help from a suitably qualified professional. If you have a restrictive diet, whereby you do not or cannot consume (m)any foods from certain important food groups, your chance of missing out on some important nutrients will be increased. You might therefore need more help in planning your dietary approach to address this.
So what’s the bottom line?
Controlling hunger is key to health and weight management. There are lots of things that can affect this, but the potentially essential role of nutrient intake is often overlooked.
Basing your diet on nutritionally dense, minimally processed foods (whichever dietary approach you are following) can help you meet your body’s need for these nutrients whilst minimising your intake of food. The resulting reduction in hunger levels and energy intake can be key in helping you manage your health and weight.
As with all our blogs and other work we’d love to hear your thoughts and feedback, so feel free to leave a comment on our Facebook page, drop me an e-mail at firstname.lastname@example.org, or tweet us/me at @XPERTHealth or @SWheatley88. If you have attended an X-PERT Programme or are an X-PERT Educator you can also register for our online forum.