A myth which is quite widespread also in bodybuilding is that, in order to lose weight, you should not consume carbohydrates for dinner. Some say after 6pm, some say after 2pm. The origin of this “dogma” is unknown, perhaps it is connected to proverbs coming from conventional wisdom such as “eat like a king for breakfast, like a prince for lunch and like a poor for dinner” or “eat double breakfast, share your lunch with a friend and give your dinner to your enemy”. However, these popular beliefs refer to the amount of food, probably in relation to the slowdown of metabolism and to the digestive capacity of the gastrointestinal apparatus: after 10 pm, it tends to shift to functional rest and it should not be overloaded in order to guarantee optimum organic recovery. Yet, these sayings do not distinguish between carbohydrates and proteins. Probably bodybuilders and wellness-oriented people – who are very careful about their glycaemic regulation – consider insulin as a fattening hormone and are afraid that the potential insulin peak in the evening, caused by a meal rich in carbohydrates, may jeopardize their effort in keeping fit. In fact, a study by Jacobs and colleagues, published in “Chronobiology” in 1975, confirmed this, demonstrating that a normal-calorie diet given to people with normal weight and made of just one daily meal of 2000Kcal taken in the morning caused weight loss, which did not occur if the same meal was consumed in the evening. On the other hand, Caviezel and colleagues, in “Obesity: Pathogenesis and treatment” in 1981, demonstrated that the evening intake of a daily single meal of 600 Kcal in male obese people caused a higher weight loss than the same meal consumed in the morning. Therefore, it is clear that the two studies present a different result. However, they were performed on different types of subjects: the first one on normal-weight people, the second one on obese people. Do obese people have a different chrono-metabolic response? Actually, a new study performed on 78 Israeli policemen in April 2011 supports this hypothesis.
Sofer S. and his team at the Faculty of Agriculture, food and environment of the Institute of Biochemistry and Nutrition Science at the University of Jerusalem (Israel) have carried out a study in order to determine the effects of a low-calorie diet with carbohydrates consumed mainly for dinner. The study involved 78 overweight policemen, with a body mass index over 30 (the body mass index is a parameter of the height/weight ratio which gives the measure of how far we are from our ideal weight). The policemen, according to the abovementioned parameters, were obese with android or hyperlypogenetic characteristics. The subjects of the study were divided in two groups based on a causality criterion. Each group followed for six months a diet of about 1300-1500 Kcal., made for about 20% proteins, 30-35% fats, 45-50% carbohydrates. The experimental group consumed carbohydrates mainly for dinner, while the control group consumed them in the various meals during the day. Basically, the experimental group was following a low-carb diet during the day, consuming carbohydrates mainly at dinner. Dinner for the experimental group consisted in two possible alternatives:
a) 2-4 slices of bread + 2 spoons of fresh spreadable cheese or a slice of processed cheese, half a tin of tuna, mixed salad, a spoon of olive oil or one quarter of avocado, a fruit yoghurt or a diet ice-cream or two biscuits or a sweet.
b) A portion of rice, pasta or legumes or 1-2 potatoes or 1-2 sweet potatoes, a spoon of meat sauce (gravy), cooked vegetables or mixed salad, a spoon of olive oil or a quarter of avocado, a fruit yoghurt or a diet ice-cream or two biscuits or a sweet.
In any case, not really a “healthy” diet or a diet for athletes, but it is important to consider that the subjects of the study were overweight and that, overall, it was a low-calorie, slimming diet. The results of the study, shocking for the majority of people but not certainly for me, are the following: higher weight loss, with consequent reduction of the waistline and of the fat mass, were observed in the experimental group which had consumed carbohydrates mainly at dinner compared to the group which had consumed carbohydrates throughout the day. Moreover, it was also possible to find considerable improvement in glycaemia on an empty stomach, in insulin resistance, in the total cholesterol – LDL and HDL (that is, the so-called bad cholesterol decreased while the good one increased) – and in the inflammatory markers (protein C – reactive (PCR), tumour necrosis factor – a (TNF – a) and interleukin -6 (IL-6). (Sofer S. Eliraz A. Kaplan S, Voet H. Fink G, Kima T, Madar Z, Greater Weight Loss and Hormon Changes After 6 Months Diet With Carbohydrates Eaten Mostly at Dinner. Obesity, (Silver Spring), 2011 Apr 7, (E-pub, ahead of print).
The authors of this study believe that these results, in the group which consumed carbohydrates at dinner, were caused by a higher production of adiponectin, an anti-inflammatory hormone. This would explain the decrease in inflammatory markers and the improvement of insulin resistance. Also, the stimulation of leptin – an anorexiant hormone – due to the peak of insulin caused by an evening meal rich in carbohydrates is said to favour a higher level of leptin throughout the day, which would cause lower food intake.
Let us talk a little bit about leptin, the so-called satiety hormone, secreted by the adipocytes of the adipose tissue. It was seen that people with leptin deficiency take more calories; those who do not produce leptin have an increase in hunger and an altered mechanism of satiety. When these people who lack leptin are given leptin, their hunger decreases.
The reduction of leptin, which occurs on a low-calorie diet, signals a nutritional deficit which causes the increase of hunger to compensate this deficit. This is why bodybuilders are always so hungry when they take part in a competition, above all if the follow low carb diets. When leptin decreases, some adaptation mechanisms occur aiming at survival: the metabolism decreases, vitality decreases, so we have less and less energy, and the hypothalamic – pituitary – gonadal axis, also in charge of reproduction (diminished production of testosterone and estrogens), is inhibited, since in condition of lack of food it is not advisable to waste energy to have children who would probably have to deal with subsistence issues. Basically, insulin is the hormone which stimulates the production of leptin and, actually, the consumption of a free meal rich in carbohydrates once in a while can favour weight loss, favouring the production of leptin and stimulating the metabolism. The fact that insulin – and not glucose levels – stimulates the production of leptin is demonstrated by the fact that people with insulin-resistance – that is, people who have high levels of insulin despite having normal glycaemic values – show higher levels of leptin. The problem is that these people, especially if obese, also show leptin-resistance, so the possible amount of leptin does not cause the desired anorexiant results. Another hormone involved in regulating the appetite is Ghrelin, which is secreted mainly by the stomach and pancreas and it is complementary and antagonist to leptin, since it has an orexizant effect, that is, it stimulates one’s appetite. By stimulating the hypophysis, Ghrelin also stimulates the secretion of the growth hormone, and also of prolactin and ACTH (adrenocorticotropic hormone), it inhibits the pituitary – gonadal axis and has a negative influence on sleep. The activation of the hypothalamic – pituitary – adrenal axis leads to a higher production of cortisol, the hormone which regulates the adaptive response to the various sources of stress also through food choices. Ghrelin is suppressed above all by a meal rich in carbohydrates, since it is insulin which inhibits its production. Actually, in people with insulin-resistance the regulation of the secretion of Ghrelin, after a meal rich in carbohydrates, is altered. Among other things, Ghrelin acts on the metabolism of fats, diminishing their use, but this apparent contraindication is instead coherent with a condition of shortage, when the goal is finding food through motivation given by the stimulus of hunger and saving deposit fat as a precious source of energy. At this point it is natural to consider this: if the key to this study were leptin stimulation, as the authors claim, whose effect would be above all modulating the appetite which certainly has a very important role on the possibility to follow a diet, this does not justify the fact that the people whose dinner was based on carbohydrates lost more weight than those who consumed carbohydrates in the other meals (with the same daily total calories (1300.1500), and the same can be said for the study by Caviezel which was based on the consumption of only one evening meal of 600 Kcal. Well, there must be some other factor! Here follows cortisol: these obese people probably belong to the hyperlypogenetic morphotype, characterised by android obesity with prevalence of the activation of the hypothalamic – pituitary – adrenal axis, hence with higher production of cortisol. Well, several studies carried out on animals and humans have demonstrated an inverse relation between cortisol and leptin. High cortisol and low leptin are a characteristic both of animal models of depression and of people suffering from mood disorders. Moreover, carbohydrates favour the production of serotonin and, consequently, of melatonin, which inhibits the production of cortisol. Therefore, if the acute effect of cortisol promotes the oxidation of triglycerides, in the long period it causes an increase in food intake and, since it causes hyperglycaemia, it favours insulin resistance, thus causing an increase in the body fat, above all at visceral level, central level and on the back. It is common to know someone who, after a prolonged therapy with corticosteroids (ex. cortisone), put on weight without changes in their food habits. Hyperlypogenetic people with prevalence of the hypothalamic – pituitary – adrenal axis show since the early morning particularly high levels of cortisol which tend to cause an increase in glycaemia, so it is not uncommon to find quite high levels of glycaemia on an empty stomach. If too many carbohydrates are consumed in the morning, glycaemia further increases with quite a fattening insulin stimulus, since it finds as a substratum both the glucose deriving from the meal and the one produced by gluconeogenesis produced by cortisol. On the contrary, the insulin stimulus of a meal rich in carbohydrates consumed mainly in the evening and preceded by low carb meals finds a situation of low levels of glycogen both at hepatic and muscular level – above all if the person has also performed some physical activity during the day – and a low level of glucose in the blood. So, insulin stimulation caused by the carbohydrates in the evening meal favours synthesis above all of the supply of hepatic glycogen, and it activates all those mechanisms of hormonal regulation mentioned before concerning leptin, Ghrelin, serotonin and therefore cortisol, which will stimulate easier weight loss and less hunger. This fact is not irrelevant even if someone may say “I don’t care about being hungry if I get a result in the end”. Actually, the problem is that chronic “hunger” causes chronic stress and the secretion of cortisol caused by chronic stress favours the increase of visceral abdominal fat even more than subcutaneous fat. Visceral fat is particularly easy to spot, since it is associated to insulin resistance, hypertension, cardiovascular diseases and diabetes. Therefore, the mental stress coming from food restrictions with low “compliance” causes an increase in the secretion of cortisol, which further increases the appetite and favours the increase of abdominal fat. Certainly, in hyperlypogenetic people with correlated cortisol-responder-stress, the meal more at risk is dinner, when they feel the need to relax and, as a consequence, the consumption of carbohydrates in this meal helps their “compliance” towards the diet also with the same amount of calories taken daily. This helps the reduction of the levels of stress and cortisol, which already tend to be high.
Then, do we have to reverse the old saying “eat like a king for breakfast, like a prince for lunch and like a poor for dinner”? Or do we have to interpret it in a different way, considering that in the past meat and game, that is, proteins, were above all a prerogative of the rich and nobles, while the poor stuffed themselves with carbohydrates, that is, bread? So does “have dinner like a poor man” mean have carbohydrates for dinner? This hypothesis is obviously an exaggeration, yet it is certainly true that there is not a unique standard of healthy diet. A diet must be customised according to one’s sex, genetic predisposition, individual biorhythms, environmental conditions. That is, according to the concepts of the chronhomorphodiet or COM Diet.
OLYMPIAN’S – January/February 2014