Chronobiology, or the science that studies biological rhythms, has led to the formulation of the chronodieta, a food strategy based on the time of food intake.
This dietary strategy is based on the circadian variations of different biological functions, which in turn are based on the hormonal variations during the day.
In short, it is not only important to ask oneself how and how much to eat but also when to eat .
Chronodiet and Hormonal Control
Hormonal control is the premise on which not only the chronodiet, but also most of the latest scientific research on nutrition and weight loss is based. The much loved and discussed Zone Diet is one example. According to these theories, the assimilation of nutrients and the consequent metabolic variations depend on a complex network of hormonal adjustments.
There are hormones that favor the accumulation of body fat and the loss of muscle mass and others that favor the disposal of body fat and the acquisition of muscle mass. Stimulating the secretion of one or the other hormone with the diet means reaching one’s goals or not; not only that, it is important to evaluate individual hormone levels as some subjects can manifest a natural over or underproduction of certain hormones.
Time Slots for the Assumption of Various Foods
In the chronodieta, conceived in 1992 by two Italian doctors, it is recommended to take carbohydrates at the beginning of the day.
It is therefore not a question of only limiting their intake but also of distributing their intake throughout the 24 hours, concentrating it in the morning and early afternoon.
Bread and all other foods with a high carbohydrate content must therefore be taken in the morning since in this phase of the day the liposynthetic and anabolic action of insulin is counteracted by corticosteroid hormones ( cortisol ). Not only that, the activities carried out during the day allow you to metabolize a large part of the energy introduced with food in the first part of the day.
Carbohydrates for Lunch, Protein in the Evening
If on the one hand it is important for the supporters of the chronodiet to reduce the intake of carbohydrates in the evening hours, on the other hand the protein consumption must be increased during this period of the day.
The hormonal profile that is established in the evening favors the use of fats for energy purposes and the building of muscle mass during the night.
The following table shows the main hormones on which the chronodiet is based, for each the function and the circadian rhythm are indicated
| HORMONE | FUNCTION | CIRCADIAN RHYTHM | PRINCIPLES OF THE TIMELINE |
| GH | Promotes protein synthesis (increases muscle mass) and stimulates lipolysis (use of fats for energy purposes) | It reaches its acrophase around 24 and records its minimum values from 8 to 20 | Protein consumption should be increased in the evening to promote the building of muscle mass |
| CORTISOL | Promotes the loss of muscle mass (especially in the lower limbs) and at the same time promotes the accumulation of fat in the abdominal region | Maximum peak (acrophase) recorded around the very first hours of the morning (3-4) and minimum peak that coincides with the first hours of night rest (22-24) | Carbohydrates should be taken in the morning as in this phase of the day the liposynthetic and anabolic action of insulin is counteracted by the high levels of cortisol |
| INSULIN | It is the anabolic hormone par excellence, it favors the synthesis of glycogen, proteins but also fats; it is a hypoglycemic hormone that is, it lowers blood sugar | Virtually absent, with a marginal role, its main regulator is blood sugar, or the amount of sugars present in the blood | Promotes the accumulation of fats; it is activated by a meal rich in carbohydrates that must be taken in the morning to counteract its actions thanks to the high levels of cortisol |
| GLUCAGON | It is a hyperglycemic hormone, an insulin antagonist and promotes the raising of blood sugar | Virtually absent, with a marginal role, its main regulator is blood sugar, or the amount of sugars present in the blood |
THE EVOLUTION OF THE TIMELINE
At its origins, the chronodiet was in effect a dissociated diet , a diet that imposed not only the consumption of certain nutrients at particular times of the day, but also the prohibition of taking foods of different origin in the same meal (for example, it was necessary to separate the consumption of carbohydrates from that of proteins).
Obviously, such a drastic method can only have some negative implications. The following table shows the pros and cons of the chronodiet.
Positive, Negative and Questionable Aspects
| POSITIVES | DOWNSIDES | DISCUSSIBLE ASPECTS |
| Consume food by distributing it in 4-5 daily meals Importance of breakfast The evening meal must be sufficiently detached from the moment of sleep It is necessary to avoid food intake during the night hours | It is not necessary to weigh the various foods and there is a certain freedom in the quantities of foods to be consumed as long as they are taken at set times. It is proposed as the ideal diet for many categories of people in reality, there are many cases in which such a dietary approach is not recommended. Little space for the culinary tastes of the subject who is forced to eat not according to his wishes but according to his own watch | Prefer whole foods to refined foods Eat fruit, cereals and all foods rich in simple carbohydrates by the early afternoon Among the carbohydrates prefer rice and corn Eat whole foods rather than refined To better digest carbohydrates, thus obtaining less fat accumulation, do not associate them with protein foods such as fish , eggs and meat (especially pork) At dinner prefer proteins, avoiding carbohydrate intake Do not drink wine , beer and coffee in association with carbohydrates Remember that lunch must be the most important meal abundant Consumeseasonal fruit and vegetables |
In the following table we see how it is possible to make positive some criticizable principles of chronodiet
| FROM CRITICABLE | A POSITIVE |
| Eat whole foods rather than refined ones. | In the absence of contraindications, prefer whole foods rather than refined ones, making sure that these come from controlled organic sources |
| Eat fruit, grains and all foods rich in simple carbohydrates by the early afternoon | In the absence of contraindications, it is recommended to limit the ingestion of simple carbohydrates at dinner by preferring complex ones ( whole grains , unsweetened vegetables and fruit ). |
| Among the carbohydrates prefer rice and corn | In the absence of contraindications, consume mainly complex carbohydrates such as bread, pasta, rice and corn, reduce the consumption of simple sugars |
| To better digest carbohydrates, thus obtaining less fat accumulation, do not associate them with protein foods such as fish, eggs and meat (especially pork). | The association of carbohydrates and proteins leads to a lengthening of digestion times which favors the fermentation of sugars and the onset of gastrointestinal problems in some individuals |
| At dinner, prefer proteins, avoiding the intake of carbohydrates. | At dinner, especially if consumed shortly after the night’s rest, favor proteins by limiting the intake of carbohydrates. |
| Do not drink wine, beer and coffee in association with carbohydrates. | Limit the consumption of alcoholic substances; coffee does not facilitate digestion , on the contrary it increases gastric acidity . |
| Remember that lunch has to be the biggest meal | Consume foods by distributing them in 4-5 daily meals, two main (lunch and dinner), one intermediate (breakfast) and 1 or two minor meals (snacks) |
| Consume seasonal fruit and vegetables | Preferably consume seasonal fruit and vegetables; make sure of their origin by carefully reading the labels ; avoid foods from non-EU countries where controls on the use of pesticides are reduced |
Another important aspect to consider is individual variability, for example some people usually eat dinner after returning from work and then go to the gym a few hours later, a similar argument for shift workers , or for those who continue to late into the night; in all these cases the principles contained in the chronodiet are not applicable and also the evening meal must contain, for obvious reasons, carbohydrates in good quantities.
Also be careful not to demonize corticotropic hormones at all costs, as the main lipogenetic hormone (which favors the accumulation of fat) is not cortisol but insulin . Taking too many simple sugars (or sugars with a high glycemic index ) causes at any time of the day an overproduction of insulin necessary to counteract the glycemic increase. It is debatable to say that during morning hypercotisolism it is useful to take many simple carbohydrates as hypercortisolism favors hyperglycemia .which will be further augmented by a carbohydrate-rich meal; increasing blood sugar means increasing insulin secretion with all the negative consequences that we have previously listed.
In addition to an easier accumulation of fat, hyperinsulinemia contributes to the premature onset of the sense of hunger ; on the contrary, the consumption of a balanced meal, in addition to keeping blood sugar and insulin levels relatively constant, slows down digestion and helps to give a general sense of satiety.
The last point to consider is that in the late afternoon the highest peaks in body temperature are recorded and consequently the energy metabolism is very high. Therefore it would not be so wrong to continue taking carbohydrates even in the early and late afternoon, limiting them only in the evening meal.
Extrapolating the Positive Elements
There is no perfect diet , there are correct eating habits, there is information and there are contraindications, for these reasons the main rule is, and remains the same, to consult a specialized doctor before embarking on any diet program.
The chronodiet, as we have seen, contains several positive points that must be extrapolated and included in one’s technical and cultural background. On the other hand, however, it is not without incorrect aspects and extreme concepts that must therefore be abandoned.