See Management, Treatment and Prevention.

Obesity is more than a number.  As defined by the Obesity Medicine Association, it is a ” chronic, relapsing, multi-factorial, neurobehavioral disease, wherein an increase in body fat promotes adipose tissue dysfunction and abnormal fat mass physical forces, resulting in adverse metabolic, biomechanical, and psychosocial health consequences”. It is therefore not “cured” simply by the numbers getting better.

Obesity is associated with a range of problems, including slipped upper femoral epiphysis and sleep apnoea that are clearly related to being overweight, plus psychological issues related to self image.  But there are also unexpected complications such as higher rates of admission and longer hospital stays after road traffic accidents, and higher mortality with asthma and SARS-CoV2 (but not an increased risk of getting it).

It does appear that adipose tissue produces inflammatory cytokines.  The insulin resistance that can be associated with obesity also increases endothelial and platelet dysfunction, which increases the risk of vascular and thrombotic conditions.   

Hazard ratios for healthy lifestyle factors and BMI - BMJ 2016It’s also true that BMI is only one factor in health – if you have one or more healthy lifestyle factors, you could well have better life expectancy than someone with normal BMI but high waist circumference and no healthy lifestyle factors. [BMJ 2016] Evidence that moderate/high levels of cardiorespiratory fitness appear to attenuate or even eliminate the risks.

Some US states reporting declines in rates of childhood obesity. Australia has plateaued. The COVID pandemic was bad for obesity with figures from NHS England and Public Health Scotland showing a sharp increase – obesity prevalence at reception age (4-5yrs) is up from 9.9% in 2019/20 to 14.4% in 2020/21, and Year 6 (age 10-11), from 21.0% to 25.5%. 

Ethnicity is a major risk factor – Black and Asian have higher rates than whites, Chinese lower.  Boys outnumber girls slightly in both age groups.  Risk at least twice as high in most deprived areas cf least deprived.  In London, 30% of 10-11yr olds now obese.

Obesity and Child Protection

Growing evidence linking adolescent and adult obesity with childhood sexual abuse, violence and neglect. In US preschool children, obesity linked to neglect and physical punishment even after controlling for socioeconomic group.

Wouldn’t be surprising if food became a way of dealing with stress (or feeding a way of dealing with distress) but obvious confounding.

A study of obese children in care found only 1% of the obese children were obese when taken into care, and risk increased with time in care. So can hardly be argued that putting children in care likely to help severely obese children!

So probably not itself a child protection concern, but may be part of wider concerns. Development of obesity and then failure to tackle also 2 different things. Consistent failure to engage with lifestyle changes or outside support IS a sign of neglect. Parental capacity is important. Environment often very unhelpful.

If looked at from children’s rights perspective, health can be seen as shared responsibility of the state, parents, and child themselves – note right to health, play, safe spaces, clean air etc. [ 2016]

Obesity Detection

About half of parents of overweight/obese children fail to recognise it. Particularly true for young children.  Doctors are not great at perceiving obesity visually either – in small study of 100 patients, 19% of obese were underestimated, and 25% of overweight [BJMP 2012;5(2):a520]. When presented with photos, GPs incorrectly assessed the majority of obese and about half the overweight patients presented in photographs. To be fair, this poor performance is probably true of the general population too.

BMI vs Fat

There are probably different obese phenotypes.  BMI is only a moderately good predictor of adiposity in children, and poor in younger children.  It is also true that there appear to be ethnic differences, for example Indian boys tend to have relatively higher percentage fat at all BMI levels.

Abdominal circumference in adults probably more important when it comes to metabolic (type 2 diabetes) and cardiovascular risk. Triceps skinfold thickness centiles available, over 14-15mm 95th centile for under 8 boys, 15-20mm for under 8 girls, 16-23mm for over 8 boys and 21-30 for over 8 girls.

When it comes to monitoring, changes in BMI have reasonable sensitivity but poor specificity when it comes to changes in adiposity – so beware over intepreting [BMC Ped 2018].

Weight (self) Perception

Weight (self) perception has a complicated relationship with actual weight, and whether young people engage in extreme weight management practices.  People who were underweight or overweight were mostly aware of their weight (80%, 96%), but bizarrely over 80% of those of healthy weight and obese inaccurately assessed their weight. Overassessors with healthy weight more likely to have extreme weight management practices, and even more true if underweight and female (OR 12.6, 95% CI: 3.4–46.6). [n=14,722 US high-school students, J PedGN 2014]

40% of men don’t recognise that they are overweight/obese (cf 19% of women), esp lower social class and ethnic minorities (“visual normalisation”). And seems to be getting worse over time.  [England, Obesity 2018]


Sleep deprivation

Associated with short duration of sleep in several cross sectional studies.  Longitudinal study in NZ 3-5yrs old found longer sleep reduced BMI at age 7 by 0.48 per extra hour, with a 61% reduction in risk of being overweight.  Controlled for physical activity, diet etc.  BMJ 2011:342:d2712.  Late bed times (after 9pm) an independent risk factor (for waist measurement) in age 2-6 [Sweden, Peds 2020].

Screen time

More TV time associated with increases in BMI from ages 14-18 in White middle class American kids with starting BMI average or above average.  Obesity 2013 Mar; 21(3): 572–575. doi:  10.1002/oby.20157]

Having TV sets in bedrooms associated with excess weight gain.

  • In France, in boys only. Explained 26-42% of body adiposity, other leisure activities didn’t make much difference. [Obesity 2017]
  • In US, boys and girls. 30% higher risk of being >85%, even after controlling for TV time! [Peds 2002]

Interventions to reduce screen time have also reduced obesity (not because more physical activity – less snacking!) [2yr study of age 4-7.  Success higher in lower social class] Epstein LH, Arch Pediatr Adolesc Med. 2008;162:239-45.]

These things all go together of course –

  • The cluster with the most screen time, shorter night-time sleep duration, average dinner timing and outside playtime had the highest overweight/obesity prevalence (15.1%)
  • This cluster also had the highest proportion of irregular mealtimes and the most screen time for both parents.
  • Cf cluster with the least screen time, the longest sleep duration, the earliest dinner timing and average outside playtime (4.0%).
[Japan, BMJ Open 2016]

Physical activity

Most people overestimate their own levels of activity, compared with accelerometer recordings.  Fitness helps boost mood, which can positively influence diet adherence.  Muscle mass will increase calories burned even at rest.

When it comes to losing weight, physical activity really needs to be at the high intensity level to be effective, especially if dietary changes are limited.

The concept of regular exercise or sport is both alien and inconvenient to the majority of the UK population. In recent years, rhetoric has
switched from sport to physical activity.


People who identify themselves as overweight have worse mental health, for example greater risk of depression and reduced quality of life.  Not sure if there is any evidence for this in children but this presents a major problem when it comes to trying to improve health outcomes. [ObesRev 2017]

Obesity among Health care professionals

In England at any rate, nurses are no more likely to be obese than people in non-health professions (25%) but more likely to be obese than other health care professionals.  Unregistered care workers have the highest rate of obesity (31%) [BMJOpen 2017].

Health professionals of normal weight are more confident in their weight management practice, perceive fewer barriers to weight management and have more positive outcome expectations, and have a stronger role identity.  But also have more negative attitudes towards obese individuals.

Being female and having  knowledge and clinical experience of weight management appeared to predict positive attitudes towards obesity/obese patients and high self-efficacy in weight management. [ObesityReviews 2011]