Resumen: The stability of body weight and fat composition depends on several
components such as food intake, nutrient-associated turnover, thermogenesis, and
physical activity. These elements underlie complex interrelated feedback mechanisms,
which are affected by personal genetic traits. A number of investigations
have evidence that not all calories count equal and that some specifi c biofactors
occurring in foods may affect energy effi ciency and fat deposition. Thus, the role of
protein and specifi c amino acids, the glycemic load of different carbohydrates and
foods, the type of fat, as well as the involvement of some food components with
bioactive functions affecting the energy equation are being ascertained, since they
can infl uence body composition and adiposity.
Indeed, moderately high protein intake, carbohydrate with low glycemic index, n -3
fatty acids, calcium, and some thermogenic substances and antioxidants have been
found to possibly contribute to reduce the body fat content. Many of these fi ndings
have been supported not only through epidemiological studies, but also by animal and
cell investigations as well as through controlled nutritional interventions in humans.
A better understanding of the putative involved mechanisms in the effects of
individual fatty acids such as conjugated linoleic acid, eicosapentaenoic acid, and
docosahexaenoic acid in body composition maintenance, as well as the identifi cation
of new bioactive compounds affecting lipid turnover and energy metabolism
will open the way for a better control and management of fat deposition in different
stages of the life cycle, since some of them are able to control relevant metabolic
pathways at the molecular level.
