Almost one third of male adolescents inaccurately perceive their weight. This can influence their eating habits and, consequently, their health, according to a study led by the UAB and conducted with 600 teenage boys from Barcelona and surrounding areas. Up to 25% of the boys reported trying to lose or control their weight in the past year.

The research, conducted in collaboration with the Mental Health Unit of the Parc Taulí Health Corporation (CSPT), analysed the effects weight perception had on the boys' behaviour when trying to lose or maintain their weight. Researchers measured the height and weight of the boys in situ. A total of 597 teenage boys aged 13 to 16 years participated. They predominantly came from middle-class families of Spanish origin, although the research also included boys of Latin American, North African, European and Sub-Saharan origins. They were also asked what they thought their weight level was - underweight, normal weight, slightly overweight, very overweight - and if they had dieted in the past year, as well as what things they had done to lose or control their weight. A total of 65% of them had a normal weight level - according to their Body Mass Index - and 19% were overweight, 7% were obese and 8% were underweight.

The research discovered that up to 28% of the participants were inaccurate on estimating their weight status. Among those with a low weight status, 43% overestimated their weight level, while 86% of those who were obese underestimated their real weight status. Among those who were slightly overweight, 40% underestimated their weight status and believed they had a normal weight. The majority of boys with a normal weight status (85%) were accurate in their perception and 5% perceived that they were overweight.

"We've discovered that if a teenage boy with normal weight perceives that he is overweight, the possibilities of him going on a diet are as high as if he really was overweight. And something similar occurs with unhealthy weight-control behaviours, such as skipping a meal or eating very little food. In this case, the probability of doing these things is as high among those who are overweight and those who think they are", explains Carlos Almenara, lecturer in Psychology at the Masaryk University of the Czech Republic and main author of the study. "These are particularly important discoveries when we consider the high percentage of adolescents who are trying to lose or control their weight, given that 25% informed us of having gone on a diet at least once in the past year or of having unhealthy weight-control behaviours".

Researchers considered that many adolescents could be behaving in an unhealthy manner in order to lose weight or maintain their weight, because few adolescents have the guidance of a professional. This would lead to acquiring unhealthy eating patterns. In addition, a diet without any professional supervision or a diet associated with extreme behaviours can lead to a lower intake of nutrients which are essential for this developmental period.

Sociocultural Factors

With regard to factors which can influence an inaccurate perception of one's weight, experts point to sociocultural factors. "We believe underweight boys who perceive themselves as having a normal weight or being overweight might have incorporated an ideal of male beauty based on a thin but toned body. In the case of overweight teenagers who consider their weight normal, it may be because they perceive messages on obesity as something socially undesirable. For this reason, they do not accept the fact that they are overweight although, at the same time, the fact that they are dieting is a sign that they are making efforts to stay within their group's norm", comments David Sánchez-Carracedo, researcher of the Department of Clinical and Health Psychology of the UAB in charge of coordinating the research.

Alternatively, the study considers that given the increasing number of overweight and obese adolescents in Spain (27%, according to the study), a relatively small number of these boys may perceive that being overweight is the group's norm, and therefore consider their own weight status and normal, in which case they do not diet at all.

The study highlights the importance of promoting healthy eating habits among adolescents, without making weight loss the foremost objective.

"Professionals must also bear in mind that an inaccurate perception among overweight boys may represent an obstacle during the treatment. Underweight boys who believe they are overweight could indicate that they suffer from an eating disorder or have a higher risk of developing one in the future," Carlos Almenara concludes.

Few Studies with Boys

Most studies focusing on weight perception have been conducted with adolescent girls. The few to have included boys analysed all participants together, without taking into account differences between underweight and overweight boys. When comparing girls and boys, the latter tend to underestimate their weight status whereas the former tend to overestimate theirs.

"In our study, which as in any other also has its limitations, we used exact height and weight measurements for each adolescents and international criteria for the classification of each individual into their corresponding weight-status category", Carlos Almenara explains.

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Original article: "Self-perceived weight status, dieting and unhealthy weight-control behaviors among Spanish male adolescents" Almenara, CA; Fauquet, J; Lopez-Guimera, G; Massana, M; Sanchez-Carracedo, D. Nutrición Hospitalaria. Vol. 30. Issue: 2. Pag. 301-305. DOI: 10.3305/nh.2014.30.2.7596