This is not scientific precision. This is not peer reviewed. This might not resist the rigor of an editor. These are simply observations intended to spur thought and look laterally.
Much advice about food appropriate for health has been given. Much of that has been based upon (often marginal) statistics. Many are deduced from self-reporting surveys. However the variables are so great that it is impossible to accommodate these into meaningful statistics. A few of these variables include quantum of food, types of mixtures of food, frequency of these foods, plus multiple variables related to micro-nutrients ingested simultaneously, and more.
When in doubt, it has been said, look in the instruction book. The instruction book for animals (including the human) exists in the animal. It is the inclination to eat some foods and the abhorrence of others.
Without the instruction book, one has to look at design specifications. Unfortunately the animal-machine-design did not consider the possibility of limitless food, or great food variety, or types of current cultivars. So selection by appetite might be flawed, and one is left guessing (somewhat) about the design specification. That is what is addressed here.
But before that, if one wants to live longer, the method has been (scientifically) available for the better part of a century. Simply, eat less. Eat less than your appetite drive. Eat less than your cohorts.
But let us look at design. Suppose humans were to be designed from scratch, which fuels (i.e. foods) should be selected, bearing in mind the limitations of availability, and knowing that the human is a mobile device with defined functional requirements and a limited life-span? Consider these options, and consider how they fit with current eating patterns:
Fat is probably the most desirable and quintessential food for humans. It is the supreme appetiser. It carries essential vitamins. Fat the highest calorific gain of all foodstuffs whilst it has a low energy cost for ingestion and digestion. It is the most cost effective source of energy. Yet fat has powerful negative feedback mechanisms. Therefore, although fat stimulates appetite it also produces satiation relatively rapidly. Rapid satiation allows food to be spread to the entire pack, in keeping with expectations of le milliere exterior which demands survival of the group, not the greedy individual. However the satiation of fat can be strongly altered by salt. Therefore, salted fat and perhaps salted protein can become “compulsive” foods, inducing the eater to keep eating until gorged. So we have yet another factor, the “additions” to food which induce compulsive feeding, prompted by those intent on making money out of food.
Protein is probably neutral tasting without the fat and salt, is not particularly palatable and does not have the “addictive” quality of carbohydrate. But it contains “essential” components which the human cannot manufacture, including amino-acids and vitamin C (curiously a “water-soluable” vitamin). It is also heavily mechanically bound to fat, and often inseperable.
Carbohydrate, on the other hand, was never particularly attractive to early humans. Yes, I know well enough that some carbohydrates, the sugary carbohydrates, are exceedingly attractive. But in primitive societies, all carbohydrates were not attractive. Pure sugar is a relatively new evolution. The current sweet fruits and even potatoes are the product of intentional selective breeding to make those carbohydrates more palatable.
The metabolisms of carbohydrate, the sugars, are again very different from fat, in that the same metabolic pathways are used for both the anabolism and the catabolism of carbohydrate. The control of carbohydrate metabolism lies outside the direct metabolic pathways, relying on end-organ control. These includes insulin receptors. This is distinct from fat where the anabolic and catabolic pathways are different, and so allowing feed-back to curb appetite and metabolic direction.
Carbohydrate’s prime quality is that it is cheap. As a consequence commerce has “wrapped” carbohydrate in both fats and sugar in order to make it compulsive eating at a cheap price. Amongst the most tempting ingestants are those that have both sugar and fat, as in chocolate.
Refined and manufacturer altered carbohydrate once ingested, prompt the desire to keep on eating it. Carbohydrate can have a long shelf life, is easily stored and so lends itself to easy snacking. No surprise that it is perfect to fuel “habituation eating”, and ultimately obesity.
Sugar is impregnated into cake carbohydrate or spread on the top as icing. Fat is used as a layer to make bland carbohydrates or even carbohydrates and protein more palatable, as in deep fried foods – where salt is added for good measure. Cheap beans are made more palatable for sale by adding the salt and sugar of ketchup.Salt is impregnated into carbohydrate ( chips and French fries).
Water, the foundation nutrient. Many children are metabolically confused because the water offered to them is laced with calories, primarily sugar and some metbolically noxious colourants. They then lose the distinction between thirst and hunger. When thirsty they might attempt to satisfy themselves by chosing “food” rather than fluid (sugar laden drinks, iced cream ). The outcome is hypercaloric habituation.
It therefore might not be what you eat, but which combination one eats, that influences the health or disease of individuals. There is some evidence that individuals like to eat the same food and will repeat eating that ingestant by choice.
“Humans like variety, humans need variety, and humans need a balanced diet”. This may not have been the case with evolutionary man and it is certainly not the case with many animals. Those animals can adapt to a particular foodstuff (obviously one that is available) and then continue eating that foodstuff by choice, even where alternatives become available.
The legend has arisen that individuals need a “mixed and balanced” diet. As far as I am aware there is no evidence that this mixing needs to occur in the same meal. True enough, one needs the vitamins and one needs the different proteins, fat and carbohydrate. But does one need them simultaneously, wrapped around each other and made into tempting compotes?