Descriptive vs. Prescriptive Nutrition

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The problem with modern nutrition science is that it is too prescriptive, too normative… it mainly focuses its efforts on telling us what we SHOULD eat. It doesn’t spend enough time studying and trying to understand our already existing eating habits. And I think it is a big problem, mainly for two reasons:

a) by not studying enough the eating habits of healthy people with healthy weight, it misses the chance to learn what kind of diet is actually healthy and sustainable… what is it about these people’s food choices and habits that allows them to stay within normal range of weight and what is it about their diet that helps them prevent diseases such as diabetes, metabolic syndrome, hypertension and heart disease.

b) by not studying enough the eating habits of overweight and obese people, it misses the chance to discover the root causes of overweight and obesity… and therefore it misses the chance to directly address these root causes. It wastes time trying to correct the consequence (extra weight) through restrictive diets where it should instead be trying to meaningfully change the eating habits that caused this extra weight in the first place, and to change them in a long term sustainable way.

I think nutrition as a science should be way more descriptive. Only through deep studies of eating habits of healthy people with normal weight we can learn what healthy eating habits are and how they lead to positive health outcomes. And when we know what these eating patterns are, we can simply copy them. They serve as a good example of how we should be eating, so there’s no reason to invent all sorts of diets, when we can simply copy what there is already and what works.

Also, only through deep studies of eating habits of overweight and obese people we can learn what, in fact, causes obesity, we can understand their eating habits as a negative example of what we should avoid. There is a proverb saying: a smart person learns from other people’s mistakes, a fool only learns from their own mistakes. Let us be that smart person – why wouldn’t we learn from the mistakes of overweight and obese people, so that we can avoid eating patterns that made them overweight and obese in the first place.

The reason why nutrition has become too prescriptive is understandable: it is informed by biochemical knowledge about nutrients, calories, metabolism, energy needs, etc. It prescribes stuff based on science… But, the problem is that theory and practice can be misaligned in the field of nutrition. What in theory sounds true, in practice might not be the best idea. A quintessential example of this stems from the early days of nutrition as a science. When it first learned about all the nutrients in food and their functions, it hoped to find a pill or artificial food that would contain all of them in good quantities, and in such a way simplify the eating and also to feed the hungry in the world. In theory it sounds enticing… just put all the nutrients there, and voila… you have a complete healthy meal. But the idea proved to be wrong, not only because there are way more nutrients in our foods than they initially believed, so putting them in one artificial meal would be much harder, but also because of the complexity of human nutrition… it’s not only about what we eat, but also, the timing, the combinations of foods, the phytochemicals which don’t count as nutrients per se, but still have important functions, the fiber, the consistency of food etc… And of course, the social and hedonistic functions of food: social bonding over a meal, and the simple enjoyment that food brings.

Today, nutrition as a science should realize, that it can’t only listen to what biochemistry and physiology tell her. Such approach would ignore the most important actor in human nutrition – our brain and nervous system in general. It’s our brain that gathers enormous amount of information from our senses and perceptions: both perceptions of food – its taste, temperature, consistency, smell, etc… and also perceptions of our internal state… how do we feel after a certain meal, how hungry we are, etc. This information then get processed in the brain to help us make choices about eating… when to eat, what to eat, and how much. Generally our brains do a good job making these choices – and for that very reason human society not only survived, but thrived and expended through centuries, without any kind of official nutrition science being there. We didn’t even know what vitamins are, let alone what their recommended daily allowances should be, yet most of the time we were getting all the vitamins that we need from our food… as our brain was guiding us correctly towards good food choices.

So my second argument is that we should have a little more respect towards our natural inclinations, our intuitions, and our naturally developed eating habits. As in theory, they should work… There our countless animal species in the world, and they all do just fine without having any knowledge about nutrition. If a dietician suggested what lions should eat, everyone would say they are crazy. You can’t tell lion what to eat, he knows it already… Biologists that study animal eating habits are much more humble than today’s typical human dietitian / nutritionist. They, in most of the cases, stick to simply describing the eating habits of animals without trying to change these eating habits in any way (nutrition of domestic animals is an important exception though). So yeah, you can’t tell a lion what to eat, but it seems, you can tell a human what to eat.

I am not saying that all the prescriptive nutrition is bad. I am just making a point, arguing that today’s nutrition is too prescriptive and not descriptive enough, and the lack of descriptive approach prevents it from learning more about healthy and unhealthy eating patterns as they already exist in the world before any kind of our intervention.

So, when should nutrition become prescriptive? When should it finally play its role in human society and give us sensible guidelines about our diets? When should it make interventions, try to make changes in what we eat? When should it stop being a passive science and become an active effort to optimize our nutrition?

Well, only when it has enough knowledge, and not only biochemical and physiological knowledge, but also empiric knowledge about how human eating patterns function naturally, so that it can give suggestions that are not only biologically sound, but that are also proven to work in practice and based on studies of our eating behaviors. Today we live in a society that is radically different from our natural habitats in which we developed our eating patterns, so today our brain can be easily tricked and confused with countless types of foods that we can choose from. Add to it all the advertisement, cultural norms etc, and you get an environment in which functional eating habits easily become dysfunctional. But not for all the people: there are still many people who manage to have healthy eating habits even in this kind of environment. These people can help us understand what we should eat, and our nutritional recommendations should, in large part be informed by what these people already do.

There is, of course, another situation in which dietetics and nutrition should intervene, even if they don’t have full knowledge about behaviors, inclinations and natural eating habits: this is the case when there is some medical disease that requires urgent intervention and in which eating patterns play an important role. In these cases, nutrition should use all the medical and biological information it has at its disposal and react quickly, so to provide support to the healing process and to prevent damage that certain kind of foods can cause to people with illnesses: for example limiting proteins for patients with kidney disease or avoidance of gluten for people who have Coeliac disease, or limiting salt intake in patients with hypertension. But in situations where we don’t need to make such urgent interventions it’s always better to wait and consider the approaches that are proven to work behaviorally as well, instead of rushing to recommendations that are based solely on biochemistry, physiology and metabolism.

Here I’ll give you a short summary regarding differences between descriptive and prescriptive nutrition:


  • is all about STUDYING AND DESCRIBING natural eating habits and patterns in both healthy and unhealthy people
  • tries to discover the underlying mechanisms that lead people towards functional or dysfunctional eating patterns
  • makes recommendations based not only on biochemistry and physiology, but also based on observed eating patterns in healthy people that have allowed them to keep good health
  • studies the nutritional CAUSES of overweight and obesity, and addresses them directly instead of trying to fix their consequences (obesity and extra weight) through restrictive diets


  • is all about telling you what you SHOULD eat (arguably based on science)
  • is mainly concerned with nutrients, calories, energy balance, and biochemical and physiological aspects of food consumption
  • does not try to study existing eating patterns that lead to positive or negative outcomes
  • makes recommendations based on strictly defined goals based on physiology and biochemistry: like you need to get such amount of carbohydrates, such amount of proteins, etc… or to lose 10 pounds we need to create a deficit of so-and-so calories…
  • tries to fix obesity and overweight directly by creating a weight loss, instead of trying to fix their underlying causes

I hope by now it’s quite obvious to most of the readers why descriptive approach is in many ways superior and why it needs to be much more often applied.

I would end by saying that Asymptotic Nutrition approach, is, in many ways, perfectly aligned with descriptive approach to nutrition. Even if it does give a recommendation based on calories, it allows you in fact, to completely model your nutrition on nutrition of healthy people who are already there, who already have body composition and weight that you’re trying to achieve. And simply by adopting their eating habits and their calorie intake, you’re not only applying descriptive approach, but you’re also on your way of asymptotically approaching your healthy weight.

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