24.02.2010 » “Chronobiological aspects of food intake and metabolism”: de zin en onzin van ‘ontbijten’ Ik trok onlangs naar onze diëtiste want ik zat ‘op mijn honger’ aangaande enkele vragen, o.a. aangaande het alomgeprezen ‘ontbijt’. Inderdaad – en mijn excuses voor de eventuele ontnuchtering – de auteur van deze website beantwoordt niet echt aan het ideaalbeeld van de sportbeoefenaar die ’s avonds om 18u zijn laatste maaltijd nuttigt, ten allerlaatste om 22u onder zijn tram ligt, om 7u uit zijn bed springt, en tegen 8u zijn eerste boterhammen al achter de kiezen heeft. Een ‘ontbijt’, wat is dat eigenlijk? Is dat de eerste maaltijd die je op een dag tot jou neemt? Is dat alles wat je vóór pakweg 10u naar binnen gespeeld hebt? Is dat hetgeen je binnen het uur na het opstaan verorbert? Is dat wat je in de loop van de voormiddag nuttigt? En hoe zit dat dan met ‘nuchtere trainingen’? Als je onmiddellijk na het opstaan een duurloop van een uur doet en daarna pas eet: is dat dan ook een ontbijt? En als je door avondlijke trainingen, werk, afspraken of consultaties een stuk later kan eten: klopt het dat “de calorieën na 18u dubbel tellen”? Wat is daarvan aan? Er zijn mensen die graag weten ‘waarom’. Op bovenstaande vragen heb ik eigenlijk nooit een afdoend antwoord gevonden. Toeval of niet: uitgerekend een paar weken terug viel er via e-mail-alert een prachtig stukje vakliteratuur in mijn digitale postbus. De essentie wil ik maar al te graag met u delen, en die vind je hieronder. Het overzichtsartikel gaat dus o.a. over ‘ontbijten’, waaronder men lijkt te verstaan – het wordt merkwaardig genoeg niet expliciet gedefinieerd – het ‘eten in de (loop van de) ochtend of voormiddag’. Gezondheid = Frequentie + Regelmaat; Leven = Ritme “Chronobiology refers to time-dependent variations in biological functions. Nearly all of them, if not otherwise proven, show oscillations over different time spans, especially 24 h. Latter are therefore defined as circadian variations. Chronobiology is time, and time has different components. These can be grouped into (i) The clock time, e.g. the time of day; (ii) The frequence, e.g. events per time span and (iii) The regularity, events at special times.” (p. 1) “A popular dietetic advice is therefore to reduce energy intake in the evening. However no scientific explanations are in general provided. Indeed only few studies have addressed this issue in the past. Also, a lively discussion between dietetians is the optimal frequency of meals eaten during the day. Should the calories divided into five portions or is better to apply to the 'classical scheme' with breakfast, dinner, lunch?” (p. 2) Gewoontes en tradities vs. wetenschap en (bio)logica “In Western societies it is usual to consume three main meals per day, i.e. breakfast, lunch and dinner. However there are major differences in the importance of the meals between different countries. Whereas breakfast is very important in Great Britain and Germany it is reduced to Coffee and Croissant or Cornetto in France and Italy, respectively. Also dinner times can markedly vary between the countries. In Germany and Austria dinner is typically between 18.00 and 20.00 h whereas in the Mediterranean regions it usually begins after 20.00 h. In addition to three main meals, people in several countries do also take snacks between the meals. Beside geographically differences one should also consider religious aspects, especially the Ramadan in Muslim cultures (…).” (pp. 4-5) OBESITY REVIEWS, January 2010 Chronobiological aspects of food intake and metabolism and their relevance on energy balance and weight regulation C. Ekmekcioglu 1 and Y. Touitou 2 1 Section of Environmental Physiology, Department of Physiology, Center for Physiology and Pharmacology, Medical University Vienna, Vienna, Austria; 2 Unité de Chronobiologie, Fondation Ophtalmologique A. DE Rothschild, Paris, France Keywords Chronobiology • energy balance • obesity • time of day Abstract Overweight and obesity are the result of a chronic positive energy balance, and therefore the only effective therapies are a diet which, on the long term, provides lower calories than the daily expended energy and exercise. Because nearly every physiological and biochemical function of the body shows circadian variations it can be suggested that also different chronobiological aspects of food intake, like time of day, meal frequency and regularity, and also circadian desynchronizations like in shift work may affect energy metabolism and weight regulation. The aim of this review is therefore to summarize and discuss studies that have addressed these issues in the past and to also provide an overview about circadian variations of selected aspects of metabolism, gut physiology and also factors that may influence overall energy regulation. The results show that a chronic desynchronization of the circadian system like in shift work and also sleep deprivation can favour the development of obesity. Also, regarding energy balance, a higher meal frequency and regular eating pattern seem to be more advantageous than taking the meals irregularly and seldom. Additional studies are required to conclude whether time of day-dependent food intake significantly influences weight regulation in humans. Honger, een natuurlijk verschijnsel: mag/moet je dat op tijd niet hebben? “A gorging eating pattern may lead to a modulation of storage and mobilization of nutrients potentially favouring lipogenesis and increase in body weight. On the other hand, eaten more often may potentially prevent metabolic fluctuations. (…) High and fast glucose absorption from breakfast meals with a high glycaemic index also can lead to a reactive hypoglycaemia inducing higher appetite and energy intake in the subsequent meal. (…) In this context, several studies showed that after larger meals, e.g. gorging, greater fluctuations of metabolites and hormones occur than after smaller, more frequent meals (89–91). For example increasing the number of meals per day can flatten fluctuations in insulin concentrations and also plasma glucose (92). Because a considerable drop in plasma glucose can induce hunger, a more frequent eating can prevent this. It may also be thinkable that more frequent eating can induce more stable and constant plasma levels of intestinal satiety hormones, such as glucagon-like peptide-1, cholecystokinin and peptide YY.” (p. 5) De Ramadan en het heilzame effect van ‘vasten’ “One of the five most important rules in Islam is that every healthy adult Muslim must hold the holy month of Ramadan. During this time the Muslim must refrain from eating, drinking, smoking and sexual intercourse from sunrise to sunset. Because the Islamic calendar is dependent on the moon phases, the timing of Ramadan changes each year (approximately 10–11 days) and the duration of restricted food and beverage intake. Food intake is restricted to the night time, resulting in disturbances of sleep and food intake. The light/dark cycle but also regular meals are important Zeitgebers that have a strong synchronizing effect on the master clock in the suprachiasmatic nuclei (d.i. een plaats in onze hersenen), as it is known that circadian dys-regulations such as in shift work can have a negative effect on energy regulation. (…) Ramadan fasting shows beneficial effects in patients with the metabolic syndrome (d.i. een typisch westers syndroom, gekenmerkt door een constellatie van symptomen zoals verhoogde bloeddruk, een verhoogde buikomtrek (overgewicht), en een verminderde glucosetolerantie). One of the primary goals is in this 'Threat of the new Millenium' to reduce weight and especially abdominal obesity, which is a risk factor. In metabolic syndrome hyperinsulinemia plays an important role in the pathogenesis. The Ramadan study by Shariatpanahi et al. showed that insulin resistance significantly improved (…).” (p. 6) And the winner is… oprecht kitische vragen stellen én zichzelf in vraag blijven stellen “All in all, in the hard scientific competition morning vs. evening, which does better, no one leaves the 'ring' as the clear winner. Breakfast has highly satiating effects but the main determinant for weight loss is the 24-h energy balance, and the few newer intervention studies did not provide evidence for a better effect of morning vs. evening ingestion in regard to loss of fat mass. However it should be mentioned that the small 'no-effect-studies' were performed in overweight/obese individuals in contrast to the 'morning-preference' studies, which included healthy non-obese individuals. It is therefore possible that genetic and/or obesity milieu-associated differences between lean vs. overweight/obese individuals contribute towards the lack of consistency between studies.” (p. 8)