Have you ever thought about why you eat the amount that you do? On the surface level, it seems like an arbitrary thing. We just accept that a certain amount of food on a plate looks like the right amount, and we don’t tend to question it much further.
Yet, even though there is basically an unlimited food supply, we usually manage to control ourselves and not eat everything in sight, and even if we did try to, at some point our bodies would stop us.
There are certain processes within the body and certain aspects of our lives that affect how much we eat.
A useful way of thinking about these is by splitting them into 2 different types of factors: homeostatic and non-homeostatic.
Your body has a huge amount of regulatory processes that attempt to keep it in equilibrium.
An easy example would be that when your mouth gets dry, your body produces more saliva, and your mouth returns to an acceptable level of moisture. If you have too much saliva in your mouth, your body won’t produce more until it needs to. It’s a bit like the thermostat in your house’s heating system. You set it at a certain temperature and if it goes below or above that temperature, the heating output will adjust up or down to get the room back to the selected temperature. The regulatory process of keeping these things close to an acceptable level is known as homeostasis, (which is where the term homeostatic comes from) and your body’s drive to stay in homeostasis can be seen in various bodily processes, one such area being its drive to stay at a certain body composition.
You can think of the homeostatic bodyfat/bodyweight regulation process as the body’s desire to make sure you have enough energy stores. After all, humans have evolved in an environment where not having enough energy stores might have meant not being able to get away from a wild animal, not being able to hunt, not being able to protect your family and many other dangerous things. Essentially, if you were malnourished, and had insufficient energy stores, you were more likely to die. Your body doesn’t quite like the idea of that, and it does all it can to make sure you don’t let our energy stores (fat) get too low.
It is thought that each person has a range of body fat level that the body perceives as safe, and this is sometimes referred to as the individual bodyfat (or bodyweight) set-point.
Your body tries to keep you at this set-point in two ways: Firstly, through a short-term mechanism of giving hunger and fullness signals, and secondly through a long-term mechanism, based on hormonal feedback.
The short-term mechanism is based on your body first giving you the signal to eat a certain amount of food, through a feeling of hunger. As you eat, the stomach fills up and expands. As this happens, the sensors in the stomach begin to send signals to the brain, based on the caloric content and the volume of food. This tells the brain that you’ve eaten enough to maintain the energy stores that it feels you require. There are other systems at play, that also send the signal to the brain that you’ve had enough food, such as the release of certain hormones, including insulin.
The long-term mechanism is essentially based on the amount of body fat that you have. Your fat cells produce a hormone called leptin. The more fat cells you have, the more leptin you produce, all else equal. Using this information, the brain assesses the amount of leptin in the blood, in order to get an idea of how much body fat you have stored. It does this so that it can assess whether you have enough energy stores (fat), or if it thinks you need more, in order to be safe. If it thinks you need more (for example, if you’ve recently lost a lot of fat), it will signal to us that we need more food in each meal, partly by making us hungrier, and also by not making signalling fullness as quickly. It also then has the double-whammy effect of signalling to you to output less energy. The combination of extra desire to eat and a down-regulation of energy output is partly what makes it difficult for most people to lose weight.
If you were to listen to our bodies hunger and fullness signals, you would probably just eat as much energy (as many calories) as you need to stay at a good healthy bodyweight, but we know that that doesn’t always happen, as can be seen by the number of overweight people that there are, and this is generally because of factors that aren’t involved in energy requirement, which are known as non-homeostatic factors.
As mentioned before, non-homeostatic factors are factors affecting your energy intake that aren’t related to a perceived energy need (or factors that aren’t related to homeostasis). They usually involve some element of eating for pleasure or to manage our emotions. This can also be known as hedonic eating.
Non-homeostatic factors are mostly related to what’s known as your food environment. This is essentially how and where food is situated and stored in your surroundings.
Again, when we look back at how humans lived 100s and 1000s of years ago, the food environment was very different. In order to get food, you had to hunt it, or harvest it, and that all required energy. So you probably weren’t going to go out and find food, unless you were hungry. Nowadays, our food is so accessible, that what would have taken a lot of time and effort to attain, can now be delivered to your door with a few clicks on our laptop. When it gets into your house, it is now easily within your reach and the likelihood is that whatever is in your house will be eaten, which is mostly true for so-called good quality foods as well as bad quality foods. This is why it is so important to manage your food environment. For example, we know that if the biscuit packet is sitting on the counter-top, on display and you see it every time you walk past, let’s be honest, it won’t be long before it’s gone. However, if it’s sitting in a packet, within a tin, stored in the bottom cupboard, even that small difference can mean you might not bother with it.
Non-homeostatic, or hedonic, eating can also affect you when you are out of our usual environment. When you go to a party, and they’re serving really tasty foods, cakes and drinks, you’re probably going to eat some, regardless of whether you’re hungry or not. You don’t want to miss out on the chance of having a pleasant experience of tasty food, plus it’s expected that you’ll eat some, and you don’t want to feel left out. This is also a problem due to the fact that a lot of these foods will be very high in calories, whilst not being filling, meaning that you tend to eat more calories than you would if you were to eat something high in fibre and protein for example. In some ways, this gets around the homeostatic hunger and fullness signalling we talked about earlier. It takes us longer to become satiated by tasty foods, and we tend to not get sick of eating if we have loads of different flavours and types of foods in a meal.
Another non-homeostatic factor could simply be the idea of eating out of habit. Maybe that could be having 2 biscuits with your 3 pm tea. Or it could be having ice-cream every evening after dinner. Or maybe you have a fizzy drink after work each day. You probably don’t need these things from an energy point of view, so therefore you aren’t eating them due to homeostatic factors, but rather that you associate them with a certain time of day or an event. These small daily habits can surely lead to overconsumption.
Also related to non-homeostatic factors effecting food intake is when we purposely monitor and restrict our food intake. Things like calorie-counting, restricting certain foods or categories of foods, fasting etc, are all examples of things that aren’t really a result of our body’s own signals telling us to eat more or eat less, but instead, we’re stepping in and regulating energy intake ourselves.
It could be said that some form of restriction is needed if you want to lose weight, for example. If you are to go with our body’s signals all the time and eat just according to them, you’ll most likely stay the same weight. After all, that is the body’s aim, and that is where it feels ‘safe’. However, when you throw in the odd bit of non-homeostatic eating, you’re likely to slowly gain weight, and most people do.
So What Can We Do With This Information?
There are a few things you can do in order to take advantage of our body’s regulating processes, and avoid the usual downfalls caused by the other, non-homeostatic factors:
Listen to hunger and fullness signals to maintain a healthy body weight. In order to do so, it can be helpful to be mindful of how you are feeling during a meal. Eating to slightly less than full may be a good idea if weight-loss is a goal. Eating sometimes when not hungry may be a good idea if weight-gain is the goal.
For weight-loss, eat high fibre and high-protein foods. These foods tend to be filling, and for a similar quantity of food, are likely to have fewer calories than something less fibrous and less protein-rich.
Eat slowly. Eating quickly can allow you to consume more calories, as the stomach takes time to send fullness signals to the brain. For this reason, and other reasons, including improved digestion, it is a good idea for most people to eat slowly.
Control your food environment. This could mean not buying food that you know you shouldn’t eat, putting those types of foods out of sight if they are in the house, making them difficult to get to, clearing out your food cupboards and getting rid of the stuff you know you shouldn’t eat, having plenty of healthy foods available at all times by preparing ahead.
Track your food intake. It can be useful to track calories or macronutrient intake for a period of time, in order to get an idea of how much you’re currently consuming. In doing so, you know that in order to lose weight, you can reduce your intake slightly, and vice versa to gain weight.
If you want to lose weight, find a nutrition plan that creates a calorie deficit, without making you want to chew your arm off. For some people, this will be a low-carb approach, or a vegetarian diet, or a paleo diet, or tracking their calories. If you are trying tot lose weight, you need to be in a caloric deficit. You should probably aim to do this in a way that doesn’t negatively impact your health, and in a way that allows you to still enjoy your life.
Conor O'Neill, Know Yourself Nutrition
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