Updated: Jan 18
You might have noticed that some foods fill you up better than others. Today’s blog looks at reasons we feel full, what helps us feel full and what might help.
You might have noticed that some foods fill you up better than others. A large chocolate muffin might have as many calories as a good-sized plate of stew, potatoes and vegetables, but most people would agree that the stew would keep you going for longer. Today’s blog looks at reasons we feel full, what helps us feel full and what you can try o understand a bit more about this.
What makes us feel full?
The way in which our body tells our brain that we are full is a complicated system that can easily be waylaid, causing us to eat more than is good for us. Despite a lot of research, it’s still not fully understood, but here are some of the things that we know are going on.
When the stomach is empty it releases hormones that travel to the brain and make you feel hungry. When you eat and food enters the stomach, it stretches the stomach wall. There are special cells, called stretch receptors, in the walls that detect this and signal the brain with feelings of fullness. These signals depend more on the amount of food rather than what is in the food, and only last as long as the stomach is full. So, the more food that enters the stomach, and the longer it stays there, the fuller you feel. So things like liquids that pass quickly through the stomach, make us feel less full and foods high in fat tend to slow gastric emptying, although whether they make us fill fuller is open to debate.
Once the food leaves the stomach and enters the small intestine, hormones are released that inhibit the hunger hormones released when the stomach was empty, and also slow down food leaving the stomach. These things take a little time to work, so people who eat quickly will often eat more before they fill full, than someone that takes their time.
There are other hormones involved as well. Body fat also produces hormones that reduce hunger. The body hasn’t evolved past the time when it needed to preserve its fat stores against times of famine, and so when valuable fat stores are being burnt it reduces the amount of this hormone produced to make us feel hungry. When we eat and refill the fat stores the hormone is increased and we fill full again. It’s possible that some people are more resistant to this hormone and others and so still feel hungry even when their fat stores are increasing.
What sort of foods make us feel full?
Some types of foods are more filling than others. But although there has been research done into this, it is fair to say that it’s difficult to make firm conclusions. There was a study done in Australia about 25 years ago now that developed something called the Satiety Index. Satiety is the technical term for how feeling full and they were trying to find what foods were most filling.
It was quite a small study with about 40 participants who were given a range of foods to eat and reported how full they felt over 2 hours. A link to the study is given below, and if you do a search on Satiety Index you will find many articles based on this study, coming to conclusions far and beyond the small size of the study and the reported difference in fullness the participants reported.
I also suspect everyone is different, so the best bet is to try out different foods for yourself and see which ones work better for you. But it’s good to have somewhere to start:
Foods that might make you feel fuller:
High protein foods such as meat, chicken, fish, eggs and cheese.
High fibre foods such as wholegrain cereal, bread, rice and pasta and pulses such as peas beans and lentils.
Foods that are bulkier and have less calories per 100g eaten, known as low energy density. Often these contain a lot of fibre or water such as vegetables, pulses and wholegrains.
Strangely boiled potatoes, which are neither high protein nor fibre were found to be very filling.
Foods that are unlikely make us feel full:
Highly processed foods are sometimes called hyper-palatable and are easy to eat in large amounts. Food companies have spent a great deal of money finding out what foods we enjoy so that we buy, eat and buy more of their products.
They usually can be recognised by having something taken out (such as fibre or water) or added (such as fat sugar, salt and other food additives). Often, they come in boxes with long ingredient lists that include things you wouldn’t use if you were cooking yourself.
Think fast food, ready meals, commercially made cakes, sweets, crisps and other snack foods. More about this in blog Why do we eat? It's not just about hunger - part one.
Liquid calories such as high sugar drinks pass very quickly through the stomach so that we don’t feel full. Alcoholic drinks in particular can also reduce inhibitions and so encourage us to eat more. Liquids that are high in fibre and/or protein such as home-made soups or milk-based drinks might fill us up better.
High Fat Foods. In these days of low carbohydrate diets, it is often stated that high fat foods are more filling. And this makes sense when you consider that they slow gastric emptying and so food stays in the stomach for longer activating the stretch receptors discussed above. But fatty foods are often very energy dense (have a lot of calories per 100g) and so it’s easy to eat a lot of calories in a small portion. It is more likely to be the high protein in low carb diets that help us feel full. These diets are often not that high in fat due to cutting out high fat/carb foods such as junk chips, pies/pasties, cakes, biscuits, sweets and pastries.
What else affects how much we eat?
It’s not just the type of food that affects how full we feel, there’s also a number of other things that might affect how hungry we get. Again, there isn’t necessarily definitive research for this, but I this list gives you some ideas to investigate what effects how hungry you get.
The time taken to eat. Taking more time to eat allows the fullness signals to get from the gut and be registered in the brain.
Attention paid to food. Having lots of distractions while eating can mean that we eat past the point when our brain is telling us we are full. Conversely if we are really busy then we might forget to eat at all.
How much we like and want a certain food, and how full we expect to be after eating it. Hormones are also released that cause us to feel satisfied after eating foods we enjoy, and enjoyment of foods can override the fullness signals and keep us eating long after we are technically full.
How much and what we have previously eaten and how active we are. If we have previously used some of our body’s energy stores, then we will receive signals to the brain that encourage us to eat more to refill them. Being active burns our fuel stores and is likely to make you hungrier to refill those stores. This may be different with different types and intensity of activity.
Some medical conditions and medications. There are medical conditions that can slow stomach emptying and so cause someone to fill full quickly (early satiety) and others such as an overactive thyroid that can make you very hungry. There are also some medications that can reduce and increase our appetite as well.
Age. Anyone who has had growing children in the house knows how hungry they get, and we do tend to have less appetite as we get older, although a very poor appetite shouldn’t be considered a normal part of ageing.
The quality of our diet. This is just a plausible theory rather something with a lot of evidence. If we are not getting the nutrients that we need from our food, for example if we eat a lot of high energy, low nutrient junk foods, we may be hungrier as our body tries to persuade us to eat the nutrients that we need. Alternatively, it may just be that nutrient rich foods are often bulky and high in fibre or protein.
Gut bacteria. Your gut contains millions of bacteria, many of which are beneficial to our health. These bacteria can affect how food is digested and stored in the body and may affect how hungry we get. So perhaps if we look after the good bacteria in our guts with the type of foods we eat, that can affect how hungry we get. Many of the foods in a varied healthy diet such as fruit and vegetables, pulses, wholegrains and fermented products such as live yoghurt and kefir also benefit our gut bacteria.
Sleep and stress. Poor sleep and stress can interfere with hormones involved in appetite causing us to eat more and possibly crave high fat/sugar foods.
Individual differences. It’s also quite likely that individuals are different, and some may feel hungrier than others. There may be people that when they have previously stored away food, for example after a blow-out meal the evening before, that their brains signal them to eat less the next day. Whereas others may have a thriftier metabolism that would rather not give up its precious energy stores and so feel hungry even if they have overeaten the previous day. This would have been an advantage when there could be a famine at any time, but not so advantageous when food is freely available at all times.
Can this be changed?
There has been much research done trying to find out what makes us feel hungry or full, and how the different hormones and nerve signals in the body work to cause this. This might involve developing new drugs or surgery or looking at what foods or behaviours around eating might cause us to eat less.
Unsurprisingly there has always been a great deal of interest in finding medication that helps us lose weight. There’s three ways this medication might work; increasing our metabolism so we burn more calories, reducing how much food gets absorbed so we absorb less calories or reducing our appetite, so we eat less calories.
I used to regularly get told about a local private doctor, who back in the 1970s would prescribe a tablet that caused great weight loss with no dietary changes, presumably by increasing the body’s metabolism. I hate to think what that was, but we’ve certainly learnt over the years that medications that rev up our metabolism tend to not be so good for the heart. Previous weight loss drugs have been withdrawn due to heart valve damage or because they have been found to increase in the rate of heart disease or stroke.
Reducing the number of calories absorbed from food has also been investigated. There are a couple of medications still on the market that reduce absorption of either carbohydrate or fat. But both of these can have unfortunate side effects. If carbohydrate isn’t digested in the small intestine it travels to the large intestine where it is fermented by the gut bacteria. This fermentation produces lots of gas, which can cause bloating wind, and even diarrhoea. Not absorbing fat can be even more unpleasant. If you eat a lot of fatty food with a fat blocker, it can go straight through you at great speed. So, both these medications only really work if you are committed to reducing the carbohydrate or fat in your diet while taking them.
Some weight loss surgery reduces the length or reroutes the gut to reduce the amount of nutrients absorbed. This can be very effective but is major surgery and shouldn’t be undertaken lightly. It also reduces the absorption of vitamins and minerals and of these may need to be supplemented long term with some types of surgery.
More recently medications have been developed that increase the amount of glucose the body loses via the kidneys after it has been absorbed into the blood. These are mostly aimed at reducing blood glucose in people with diabetes, but the glucose lost is around 200-400 Calories a day and so can lead to a small weight loss. These medications have so far had few serious side effects, although the extra glucose in the urine can lead to an increased risk of urinary infections and thrush, and a small risk of dangerously high levels of ketones in the blood in people with diabetes.
Another approach to weight loss surgery or medication is to try to find something that makes you feel fuller. This is how weight loss surgery, such as gastric bands or balloons that reduce the size of the stomach work. But it’s also been tried with medication that works on the area of the brain that makes us hungry or mimicking the hormones produced naturally by the body that slow food leaving the stomach.
Medications that affect the brain can sometimes have side effects and at least one appetite suppressant medication has been withdrawn due to low mood that increased suicide risk. So far, the medications that slow down emptying of the stomach seem to have worked without major side effects but are expensive and generally only prescribed for people with type 2 diabetes and obesity.
It’s important to understand how these methods work as they can lead to nausea or even vomiting if someone doesn’t recognise that they are full and keeps on eating. They also don’t work so well with liquids and so it’s best not to have high calorie drinks.
Also, although restricting the amount of food that you eat before you feel full can help you to reduce what you eat, hunger also isn’t the only reason that we eat. If we overeat due to stress, boredom or to cope with difficult emotions, just feeling full isn’t going to stop this alone. More about it in my blog Why do we eat? It’s not just about hunger - part two,
There is also the possibility that if you stop someone who uses food to cope with difficult emotions without dealing with the problems behind this, you are removing their coping methods, and this can lead to high levels of stress or more unhelpful ways of coping such as drugs or alcohol.
If this all sounds a bit negative, the point has not been to say that all medical weight loss methods are pointless, but more that there is no magic wand and they all require some change in behaviour to work well.
What can you do that doesn’t involve pills or surgery?
In keeping with my other blogs, this blog doesn’t really aim to tell you what to eat or promise an amazing solution so that you never feel hungry. Everyone is different, and what works for one person might not work for another. But what I would encourage you to do is some investigation into what works for you. So, it’s time to dig out the food diary discussed in previous blogs and do a bit of investigation. I have created a diary sheet for you to download, but you can also use a notebook with similar headings or design your own based on things you’d like to find out.
In an earlier blog I suggested that a food diary should include hunger before and after eating on a scale of 1-10. One would be where you feel so hungry you feel physically faint and 10 is so stuffed you feel really quite nauseous, neither recommended. Ideally you should aim to start eating between 3 and 4 (fairly to slightly hungry) and stop at 5-6 (pleasantly satisfied to full).
You are going to experiment into which foods and behaviours fill you up and keep you full and it’s also worth recording your hunger a couple of hours after a meal as well. As I have said before it’s better to not try to change anything when first doing a food diary and then introduce changes one at a time.
I am going to make some suggestions of different things to try to get you started, but you will come up with your own ideas based on what foods you enjoy.
Foods and behaviours to try.
Increase the amount of lean protein e.g. meat, chicken, fish, eggs with your meal.
Increase fibre and reduce energy density in your meal. Try increasing the amount of vegetables eaten or choosing wholegrain bread, rice, pasta or potatoes in their skin, or add pulses such as beans, peas or lentils to your meals for example adding them to stews, curries and soups.
Vegan protein alternatives might be tofu and Quorn, pulses such as peas, beans and lentils or nuts and seeds. Quorn and pulses are high in fibre as well as protein. Nuts and seeds are high in fibre, but also high in fat and so have high energy density. Vegan diets generally tend to be high in vegetables and pulses and so tend to be lower energy density, and more filing, than other diets, which is one reason why vegans tend to be slimmer on the whole (they also tend to have other healthy habits so it’s not the whole reason). However, if you want to try a vegan diet I’d suggest hopping over to the vegan society page to find out how to do this in a healthy and balanced way.
Try replacing ready meals or other processed foods with recipes cooked from scratch using no tinned, packet, or jar ingredients.
Try a full meal including a protein source, plenty of vegetables and boiled potatoes or wholegrain rice or pasta instead of fast food or grazing.
Vary the amount of fat in your meals. Search for lower fat versions of your favourite recipe, or just experiment with using less fat in your existing recipe. Commercial low-fat products are often highly processed and have extra fat and salt. Try full fat versions and whether you can manage with smaller portions of these.
Bearing in mind that it does add extra calories, you could also try adding extra fat to your food and see how full this makes you feel. Choose unprocessed natural fats such olive oil, oily fish, nuts, seeds, avocado and olive oil if possible. I promise I’ll do a blog on the Mediterranean Diet at some point, but it has the best evidence for heart health and tends to be high in these fats, fruit and vegetables, pulses and low in processed foods and so aligns quite well with the things we are discussing here. It is not, sadly, an excuse to eat unlimited pasta and red wine!
Try replacing some of your existing snacks with high protein or low energy density choices, for example a boiled egg, chicken strips, natural yoghurt, fruit or vegetable strips and hummus. Higher fat but still high in protein and fibre include nuts, seeds and olives.
Try drinking a glass of water before a meal, drinking while eating or drinking after eating to see if it makes a difference.
Replace drinks containing calories with water or tea or try having a cup of tea or glass of water instead of a snack.
Behaviours to try.
Try taking your time, eating slowly and putting your cutlery down between each bite or stopping between pieces of snacks.
Try eating a small portion and leaving 20 minutes before having more if still hungry.
Try leaving it 20 minutes before having a snack and then only having one if you still want it.
Mindful eating is a whole different topic that I will cover elsewhere, but try paying real attention to your food, look at its colour and texture, think about where it came from and how it was made, how it feels in your mouth and the taste and texture of it.
While I’m not suggesting eating foods you really don’t like, try different foods, particularly healthy foods such as different fruits and vegetables, pulses and wholegrains. Search the internet for new recipes to try. Try thinking of food as a way of nourishing the body rather than filling a hole.
If you are someone who eats irregularly or only once or twice a day, try having 3 regular meals. Experiment with not allowing yourself to get really hungry before eating.
Or if you tend to snack a lot or graze through the day not allowing yourself to get hungry, try sticking to 3 meals and see if you can manage to sometimes be quite hungry before eating.
See how a good night’s sleep or how much stress you experience during a day affects what you eat.
As I have previously said, this is about finding out a bit more about what makes you tick when it comes to eating. So, there’s no real failures with this, just finding out a bit more about yourself. If something doesn’t work, great you’ve learnt something today.
Would you like some support with your food diary? Why not book a 1;1 appointment with an experienced dietitian. Video consultations available now.
If you find that keeping a diary makes you very anxious then it might not be for you. See my previous blog Why do we eat? It’s not just about hunger - part two for more information about our emotions and eating and some sources of support with this:
Here is the appetite diary as promised or just use a notebook:
Satiety index paper
Holt et al (1995) A Satiety Index of common foods European Journal of Clinical Nutrition 49(9):675-90