## 6 Determinant Factors of Obesity
### Energy Balance  
#### 6.5.1 Caloric Intake  
One way to describe the characteristics of caloric intake is to view it from the perspective of quantity, quality, and rhythm of nutrition. The aspect of quantity of nutrition refers to the ideal absolute value of calorie intake corresponding to each age group. There is no general consensus in this regard, however, the optimal strategy most probably takes into account the level of activity for each individual and establishes optimal caloric intake accordingly. Several guidelines provide a detailed description in this respect [245; 246]. The quality of nutrition refers to achieving an optimal proportion of macro and micronutrients through dietary intake. Foods with an excessive amount of lipids and carbohydrates accompanied by a reduced proportion of protein, vitamins, minerals, and micronutrients are particularly harmful to maintaining a normal weight. The WHO recommends reducing the intake of free sugars to a value under 10% of total caloric intake, regardless of age. This refers mostly to mono and disaccharides added to food and drinks, as well as naturally occurring sugars in honey, syrups, and fruit juices. An additional reduction to under 5% of caloric intake can be warranted in certain conditions. Elevated free sugars intake frequently implies an increased overall caloric intake, which leads to weight gain. A dietary reduction in free sugars with the purpose of reducing total caloric intake leads to significant weight loss, regardless of the initial values. In studies where complex carbohydrates have been exchanged with other nutrients while maintaining the same overall caloric intake, weight reduction was not achieved [247; 248]. It is therefore most probable that the weight-reducing efficiency of free sugar intake reduction is due to the high caloric density of such foods. In consequence, a relatively modest reduction in free sugars can imply a significantly lower overall daily energy intake [249]. To this avail, sweetened beverages and \"fast-food\" should be avoided in children before reaching school age [250; 251]. On the opposing side, the consumption of fruit and vegetables provides an optimal nutrient composition, along with preferentially searching for foods with a low glycemic index to provide sources for carbohydrates, such as whole-grain foods [245]. When regarding lipid intake, lipid-rich foods such as high-fat dairy should generally be limited and an optimal ratio between saturated and unsaturated fats should be sought after. Saturated fats have a detrimental effect on weight status and cardiovascular risk. They are generally found in animal-origin foods. For this reason, it may be preferable to achieve optimal lipid intake using vegetal oils, a good source of essential fatty acids, and vitamin E. A further aspect worth considering relates to the intake of trans fats, which can increase the risk of weight excess and cardiovascular disease. Partially hydrogenated oils are the main source of trans fats. Protein intake should be achieved mostly through animal source foods with low lipid content and vegetal foods with high protein content such as beans, peas, soy, nuts, and seeds. Limitation of sodium intake should also be taken into account when considering the optimal diet [245]. When regarding the rhythm of energy intake, dividing daily calorie consumption into three main meals and 1-2 snacks is the recommended strategy starting from age two. Replacing main meals or omitting one of them with subsequent compensation, as well as frequent dining out have all been incriminated in increasing the risk for obesity [252]. Eating at irregular intervals (particularly during the night), and binge eating are typical examples of a maladjusted eating rhythm that can lead to weight excess [198,250,253]. A possible explanation concerning the deleterious effects of nocturnal calory intake refers to the inversed disposition of circadian energy expenditure versus intake.