Are GPs able to recognise obese men as obese by sight alone?

Research Paper Title

Visual Identification of Obesity by Healthcare Professionals: An Experimental Study of Trainee and Qualified GPs.


Guidelines suggest that healthcare professionals should screen and offer help to overweight and obese patients to lose weight. Despite this. such discussions are uncommon in practice. One reason for doctors lack of intervention on weight could be that they fail to recognise a person as obese.

A physician has to raise the topic of weight in the first place to record a weight, and this conversation is initiated presumably mostly on visual perception. A substantial proportion of parents of obese children underestimate their child’s weight status and healthcare professionals may be no more accurate than the general population at estimating both children’s and adults· weight status.

This study examined whether GPs and trainee GPs could correctly recognise healthy-weight, overweight, and obese males, and whether they would consider intervening with such patients. The aim was to examine the extent to which visual perception can impact on GPs propensity to treat obesity.


  • Recruitment: Between April and May 2013. 2055 GPs and trainee GPs on the lists of the UK NHS Workforce West Midlands Deanery and NHS Sandwell and West Birmingham Clinical Commissioning Group were emailed.
  • Stimuli and Procedure:
    • Participants rated 15 photographed white British males aged 18-30 years old. The photographs were evenly split between healthy-weight, overweight, and obese individuals (that is, five of each category). Models wore normal-fitting, short-sleeved shirts and trousers and were photographed standing both front – and side-on with their arms at their sides and next to a standard-sized door.
    • Participants were then informed that they would be categorising photographs of males as being underweight, healthy weight, overweight, or obese. and they should do this according to the World Health Organisation body mass index (BMI) guidelines, which were shown.
    • Participants were shown each of the 15 photographs and underneath each one they were asked to categorise the model into one of the four weight categories, estimate BMI, and select a response to “If I were this person’s GP, I would discuss their weight with them”.


Three-hundred and fifteen GPs participated with a mean age of 33.9 years [SO 8.3) and mean BMI of 24.0 kg/m2 [SO 4.7) Of these. 109 [35%) were male and 248 were GPs in training.

GPs were more accurate when classifying healthy-weight photographs than overweight or obese. They classified 4.0/5 healthy-weight, 2.4/5 overweight. and 1.7/5 obese photographs correctly.

GPs underestimated BMI associated with the photographed males· actual BMI. The mean and SD of the slope for GPs was -0.21 [0 18). with 95% Cl = -0.22 to -0 19, P<0.001, meaning that on average GPs would underestimate the BMI of someone with a BMI of 30.0 kg/m2 as being 27.58 kg/m2 (see Figure 1 for actual and estimated BMI of each photograph).

Figure 1

GPs varied greatly on whether they would be likely to intervene on weight. As expected. GPs were more likely to intervene the higher they estimated the photo’s BMI , with an OR of 1.53 [95% Cl = 1.49 to 1 58) per 1.0 kg/m2 increase in estimated BMI. Neither feeling responsible for weight management nor GPs weight consciousness were significant in the model separately or together (Table 1). There was some evidence that qualified GPs were slightly more accurate at categorising the photographed participants than the trainees. but this difference was small. The tendency to underestimate BMI associated with the photographed males actual BMI was similar for trainees and qualified GPs.

Table 1


A sample of mainly trainee GPs was unable to recognise most obese men as obese by sight alone. There was a tendency to underestimate BMI. which was more pronounced the higher the photographed subject’s actual BMI. Intervention was more likely if GPs did not underestimate BMI. The main study findings are in line with other research indicating that laypeople often underestimate body weight. One explanation for this effect may be that social norms regarding what constitutes a normal weight have altered in recent times and this makes heavier weights seem more normal and healthier than they actually are.

Most participants in this study were GPs in training. Some evidence was found that the more experienced qualified GPs were slightly more accurate at estimating weight status. This difference was small, however and there was a tendency to underestimate weight across both the experienced and lesser experienced GPs in this sample.

It is not usual to think of estimating BMI by sight as a core clinical skill. It is, after all, accurately assessed by weight and height measurement, which takes less than a minute. However, for GPs to do this they have to start talking to the patient about weight. Assessing that the patient may have a significant weight problem is an important cue for that discussion. It is important that healthcare professionals do not rely visual judgements when identifying patients who may benefit from weight management treatment.


Robinson, E., Parretti, H. & Aveyard, P. (2014) Visual Identification of Obesity by Healthcare Professionals: An Experimental Study of Trainee and Qualified GPs. British Journal of General Practice. November 2014, pp.569-570.

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