Background Obesity, defined as excess body fat can be diagnosed at 6 months. In children, BMI percentiles are used, defining the overweight between 85–95 and obesity >95. The main predictors of primary obesity in infancy are high birthweight, parental obesity, low total energy expenditure and energy intake (EI).

Aim Calculation of optimal EI in infants.

Method Calculation of estimated energy requirements (EER) for infants was made according to the formulas: [(89×Gkg)-100]+175 between 0–3 months, [(89×Gkg)-100]+56, between 4–6 months, [(89×Gkg)-100]+22, between 7–12 months. Calculation of fluid requirements was made according to Apert formula: G_g/10+200(300).

Results Were studied 11 infants 7–9 months old with normal birthweight, without parental obesity, fed with formula (76kcal/100ml) from the first month, with diversification started from 4 months, eating high-caloric foods from 5 months (100kcal/100ml), fed according to Apert formula. Seven infants had weight above the 85^th percentile and 4 of them >95^th percentile. Comparing EI according to Apert formula with EER is found an excess, increased with the beginning of diversification. Disposal of high-caloric foods, feeding with formulas with a similar amount of calories as human milk (67kcal/100ml), feeding according to EER and fluid supplementation with low-caloric beverages have led to normalization of BMI percentiles of infants at the age of 12 months.

Conclusions EI is an important predictor of infant weight. It is necessary to use formulas with a similar amount of calories as human milk. Infant feeding according to EER and fluid supplementation with low-caloric beverages lead to a normal BMI.