How can I have room for desserts even when I struggle to finish my main course? What makes me want to drink beer when I clearly regret the hangover from last weeks party? We seem to have an extreme but inexplicable liking for high calorie foods. In this post, we dive deep into our body’s functioning and reward system to explain this.
Why are we eating more?
No one gets out of bed in the morning and says, “I am going to eat so much today so that in a few years I’ll weigh twice as much as I do today.”
What happens is that our metabolism changes with age. We move less, eat more, and acquire surplus padding without realizing it. But after all these years of evolution, shouldn’t our body have some system that handles the surplus energy and tells us when to stop eating? Well, it does!
Energy homeostasis: Our built-in calorie regulator
When you systematically restrict your food intake, your fat levels drop. This tells the brain that we should eat more food and use the calories more efficiently to restore optimum energy levels. On the other hand, when you eat too much, the increased fat suppresses appetite and increases the rate of calorie usage until the body’s fat reserves have dropped back to an adequate level. Yes, we really do have a fat-burner that works better than “power-burning with green tea”.
It’s a negative feedback system that acts without your knowledge to keep the body’s fat within a certain range. It’s like a weight thermostat and is known as the “system of energy homeostasis.”
So why are we getting fatter if we have this system of controlling our body fat levels? To understand the mechanisms of how this happens, we have to look at two other systems in our brain: the reward system and the hedonistic cycle.
The reward system: why we keep going back
The reward system or cycle works by assessing the benefits of foods and reinforcing/motivating behaviors that favor acquiring these desirable foods. For instance, the first time we eat a strong cheese, we may not like it. But once digested, our reward cycle labels this as a calorie dense food that’s useful for survival. It tastes better and better every tie we eat it until we end up liking it – an acquired taste. If you doubt this, try remembering your first bitter sip of beer and how this changed into a drink that tasted good – sometimes too good.
The reward system does the same with food and drinks with addictive substances in them – like coffee or beer. Although they might taste bitter at the start, they gradually they start becoming tastier. Over time, we start buying cheese or beer because we buy them off supermarket shelves and eat the them even when we aren’t hungry just because we like them. The reward system strengthens and motivates behaviors related to foods it considers desirable.
What does the reward cycle consider desirable?
- Caloric density
- Free glutamate
- Certain textures (easy to chew, soft or crisp fat)
- Certain flavors
- Lack of bitterness
- Variety of foods
- Substances like alcohol and caffeine.
Our brains are very much in tune with these qualities, because these are all nutritious, high calorie foods. In a natural environment, our ancestors would have found it difficult to get hold of them. But in the modern world, they are used in processed food, catering, and at times even home cooking in exaggerated combinations as they overstimulate our natural reward pathways. Commercial foods are professionally designed to maximize the reward because the reward is precisely what stimulates us to buy more.
Processed foods like ice-cream, fast food, sweetened drinks, cookies, cakes, desserts, pizza, and fried foods are all exactly the kind of foods that can over-reward our behavior and are the main reason why we put on weight. Even foods sold by herbalists that are supposed to be natural can be found to contain added sugar, if we read the list of ingredients. This means that without even noticing the sweet taste, we interpret this food as appetizing.
Just to make it clear, the reward cycle in relation to food is what motivates us to look for food and put it into our mouths. In fact, if this system is blocked in laboratory animals, they stop looking for food and will eat only if we put food into their mouths.
The hedonic system: what makes us eat more
We also have a hedonic system, closely linked to the reward cycle, that is another factor responsible for weight gain. It’s in charge of controlling the amount we eat during a meal. This system is in charge of opening the entrance to the stomach a little even if we’re full, to allow for additional food. Food such as desserts that we like a lot is categorized as a palatable food (has the quality of appealing to the palate). Palatability is partly determined by innate preferences (the taste of sugar and high calorie foods) and partly by the reward system (acquired tastes).
Taken together, the reward cycle and the hedonic cycle largely determine the frequency with which we look for food, the foods we choose, and the amount we eat before we feel full.
Interaction between the different systems
The ability of the reward cycle and palatability to influence food intake and body weight is mediated by connections between the system of energy homeostasis, the reward system and the hedonic system.
For example, if we haven’t eaten for a long time, the brain notices the reduction in energy reserves (homeostatic system) and moves to increase the intake of food. This works by increasing the motivation to get food (reward) and enjoying the food when you’ve succeeded in getting it (hedonic). This is what we mean by hunger, and is largely caused because the system of energy homeostasis that activates the reward system and the hedonic system.
This connection actually goes both ways. The reward system and palatability also influence the systems of energy homeostasis so that foods that are too nice or appetizing can increase food intake despite the fact that the levels in our fat stores are telling the brain to stop eating.
We even know that overstimulation of the reward and hedonic systems can lead to addiction. Approximately 3% of the population are particularly susceptible to very tasty or pleasing foods that can actually create an addiction for these people. For the rest of the population, these foods aren’t addictive in themselves, but they can make us eat more that we should, increasing our body weight and impacting on our health.
Blame our evolution
For most of our history we’ve had to cope with too little food, so we’re very well adapted not to miss out on high calorie food. In our prosperous environment, we enhance basic foods by adding flavorings like salt or glutamate, prepare them so that they stimulate our taste buds as much as possible, and then wash it all down with sugary drinks. These same survival mechanisms are pushing us inexorably towards eating more than we need, gaining weight, and in some cases seeking happiness through food.
These mechanisms also help us to understand why very different diets can get good results. Nora Wolkow, Director of the National Institute for Drug Abuse says “the common denominator of most diets is that they don’t allow you to eat very seductive high-calorie foods that combine high levels of fat and carbohydrates.”
A recommendation about high calorie foods by Jack Lalanne
Lalanne was ahead of his time in making many recommendations in the 50s on physical exercise and nutrition that are now resurfacing. One of his best-known sayings was, “If it tastes good, spit it out!”
And so in his own way he was telling us about the influence of the hedonic cycle on food intake.
So to conclude – now we know why we eat more and get fat!
Changes in the diet over the last few decades have contributed to the obesity epidemic. The answer to this problem is both simple and challenging at the same time:
- Find our natural reward system again: like a nice afternoon with friends, developing our natural talents, like playing an instrument, instead of relying on addictive food for pleasure.
- Go back to a diet of basic home-made food flavored with ingredients that have been refined as little as possible.
- As far as possible, avoid any tastes that are too tasty and didn’t exist during our ancestors’ time.
These are just a few recommendations on how to get your energy thermostat back, self-regulate your weight like our ancestors, and sustain the healthy life that you’ve always wanted.