Well-meaning educators can cause real harm by promoting dieting and weight loss at school. This includes making statements and putting up posters saying things like “eat less & move more,” and “eat healthy foods.” Such statements are problematic from a scientific, nutrition, health, eating disorder, and social justice standpoint.
You may think you’re being helpful, but children as young as 6 years old have reported dieting, and 80% of US girls have been on a diet by age 10. Intentional weight loss of any type is correlated with higher adult weight  and life-threatening eating disorders. 
We can all agree that the goal of schools is to educate our children, so let’s all educate ourselves and learn the science before diving in with “obesity prevention” school programs that are meant to help but actually cause harm. 
But what about the “obesity epidemic?!”
Most schools that institute nutrition and exercise programs with the goal of reducing “overweight” children are doing so based on what they believe is a well-founded fear of the fact that our kids are getting fatter and fatter, and that their weight gain will result in significant lifelong health consequences. Although this concept is supported by popular belief systems and reinforced by media and health and wellness companies, it is not supported by scientific research.
1. BMI is a terrible measurement of health
The “obesity epidemic” was founded on BMI standards, which were developed in the 1800s and have been proven to be a terrible measurement of both adult  and childhood  health. The BMI standards used to define “overweight” and “obese” were adjusted for children in 2000, changing “overweight” from 95% to 85%, which resulted in an immediate increase in the number of “overweight” children with no change in actual weight to height ratio. Thus, the “epidemic” is exposed as a simple change in how statistical data is crunched.
Here is an example of people you may be surprised to find are “overweight” and “obese” based on BMI standards:
Since BMI is such a poor indicator of health, a better way to determine whether we have a true “obesity epidemic” in our children is to look at their average weights, and there have been no significant changes. “This can be taken as evidence that there has been no ‘epidemic’ of weight gain since an epidemic would certainly have affected average weights.” 
2. Fat children face no more risk of disease
Even if we were facing an “epidemic” of fatness, in a review of 17 studies, children who remained fat from childhood to adulthood had no more risk of disease than adults who had never been fat. In fact, women who maintained high weights from childhood to adulthood actually enjoyed lower levels of triglycerides and total cholesterol. 
3. It’s not as simple as overeating and under-exercising
There is no evidence to support the assumption that our kids’ weights are directly based on an energy imbalance (i.e. kids are eating too much and exercising too little), and thus can be corrected with education and motivation. Kids have shown a decrease in calorie intake , and an increase in activity rates . It is incorrect to believe that “overweight” kids are a function of simple calories in and calories out.
4. Weight loss is an unethical prescription
It is unethical to prescribe any form of weight reduction in children. The vast majority of all people who intentionally lose weight regain everything they lost and then some within three years. This is not news.
Even the International Journal of Obesity is on board with eliminating weight loss as a prescription for health. “It is unethical to continue to prescribe weight loss to patients and communities as a pathway to health, knowing the associated outcomes – weight regain and weight cycling – are connected to further stigmatization, poor health, and well-being. The data suggest that a different approach is needed to foster physical health and well-being of our patients and communities.” 
But isn’t it good advice to “eat healthy?”
Many educators may agree that children should not “diet,” but they still teach poorly-understood concepts of “healthy” eating with the goal of controlling overweight. For example, many educators tell children they should limit sugar (which has replaced fat as the current dietary demon), but the science behind this is lacking. There is very little support for the concept that sugar intake is linked to obesity.  Even sugary sodas, commonly believed to be nothing but “bad,” have no direct link to weight gain, and in fact, one study even found that teenagers who drank the most soda were thinner than their peers who avoided soda. 
Similarly, fast food has not been associated with greater obesity. Some of the heaviest populations in the world have no access to fast food.  While what children eat certainly plays a role in their health, blaming child overweight and obesity on particular foods and food groups is simply not supported by the scientific evidence. 
And while teachers may think that saying something like “eat healthy!” is at best positive and at worst neutral, they are incorrect. “Negative messages such as sugar and fat are “bad,” and the use of the term “junk food” contribute to the underlying fear of food, dietary fat, and weight gain, which precedes body image concerns and eating problems.” 
Telling children that they need to “watch what they eat” and should eat certain foods while avoiding others is absolutely not promoted by dieticians who have done the research and are familiar with what is actually healthy for our kids.
But schools should fight obesity!
It’s quite true that an alarming number of schools have decided to take on preventing “childhood obesity” as part of their mission. If the above statistics have not convinced you that it should be otherwise, then please consider an analysis of the Child Adolescent Trial for Cardiovascular Health (CATCH), sponsored by the National Institutes of Health, one of the largest school-based prevention programs thus far.
In this program, schools modified school food service, increased physical education programs, and introduced health curriculum and family nutritional education. Despite three years of admirable and well-intentioned efforts, participating schools did not reduce the rate of “overweight,” nor did they achieve decreased blood pressure or cholesterol levels. 
“There is little evidence so far that school-based programs have had a major or lasting impact on BMI or body adiposity.” 
This is likely due to the combination of two facts:
1) Weight is not directly correlated to food and exercise habits. 
2) Traditional approaches to nutrition education are focused on rules, restrictions, and requirements, which are ineffective and counterproductive. 
“Many studies over the last few decades show that when adults try to regulate or control what children eat, the children ate more, not less, and are likely to end up with weight, body image, and eating-related problems.” 
The well-intentioned attempts by schools to educate and control kids’ eating behavior is likely doing more harm than good. Controlled experiments have shown that “trying to encourage, pressure, or even reward children to eat certain foods actually turns them off to those foods and makes it less likely that they will eat them. Conversely, if children are deprived of certain foods, they become more interested in those foods and are more likely to overeat them when they get the opportunity.” 
Well-meaning school programs put kids at risk
Schools mean well when they put these programs in place, but with inadequate training and a lack of scientific evidence, they, unfortunately, do more harm than good. Considering how many articles are published about the dangers of weight and the benefits of weight loss, it surprises most people to learn that obesity researchers are still trying to figure out some of the most basic concepts in weight science, including:
1) what causes overweight (we don’t know)
2) is weight loss a necessary component of good health? (no)
3) does weight loss improve health? (no)
It is unreasonable to expect our schools to be able to teach a science that has not yet achieved data to prove that overweight is a problem, especially since scientists can’t figure out how to solve the “problem” safely and effectively. It is dangerous to put our children’s health at risk when school-based programs have no evidence of success. 
One study found that teachers who were most likely to become involved and passionate about a school childhood obesity prevention program demonstrated a very low level of nutrition knowledge as well as a very high level of personal body dissatisfaction and eating disorders.  In this study, the teachers were passionate about but not qualified to teach nutrition or weight science. Additionally, they were at risk of passing along dangerous beliefs about body weight and disordered eating behaviors.
Based on a lack of knowledge and propensity for disordered eating, it is no surprise that the majority (85%) of the teachers studied reported that they recommended strict, calorie-reduced diets despite the fact that there is no evidence to support the viability of such efforts, nor any evidence that dietary restriction positively impacts health. [16, 20]
Prevent weight stigma! (not obesity)
Instead of starting the school year with yet another “prevent obesity” campaign, schools should educate all adults in the system about the dangers of weight stigma and pursue a weight-inclusive approach.
Health researchers are increasingly calling for a complete change in the way we view weight, not least of all due to the dubious results of weight loss efforts over the past decades.  If schools are truly dedicated to helping children thrive, then they need to move from the mission of preventing childhood obesity to promoting Health at Every Size (HAES). This approach has been shown to benefit people of all sizes by focusing on self-acceptance, positive body image, healthy eating, and pleasurable physical activity.
Health at Every Size has shown “statistically and clinically relevant improvements in physiological measures (e.g., blood pressure, blood lipids), health behaviors (e.g., eating and activity habits, dietary quality), and psychosocial outcomes (such as self-esteem and body image), and that HAES achieves these health outcomes more successfully than weight loss treatment and without the contraindications associated with a weight focus. 
To prevent promoting disordered eating behaviors (and full-blown eating disorders) among vulnerable populations, educators should become familiar with the basic elements of HAES, which are:
- Bodies are naturally diverse in shape and size
- Weight loss interventions are ineffective and dangerous
- Eating should be relaxed and pleasurable and done in response to internal body cues (vs. external rules)
- Movement should be a fun, enjoyable part of life
- Health measurements must be based on a combination of social, emotional, spiritual, and physical factors (not weight alone or as a starting point)
With this approach, educators can help children of all sizes learn in a safe environment that supports their whole health and wellbeing.
References Pietilainen, Does dieting make you fat? A twin study, International Journal of Obesity, 2012  Striegel-Moore RH, Bulik CM. Risk factors for eating disorders. Am Psychol. 2007  J. Robison, Helping With Harming: Kids, Eating, Weight & Health, Absolute Advantage 7, 2007  Franzosi, M.G. Should we continue to use BMI as a cardiovascular risk factor? Lancet, 2006  Ellis JK, Abrams SA, Wong WW. Monitoring childhood obesity: assessment of the BMI index. Am J Epidemiol, 1999  Obesity and the Facts: An Analysis of Data from The Health Survey of England 2003. Social Issues Research Centre, February 2005.  Serdula, M.K., Ivery, D., Coates, R.J. et al., Do Obese Children Become Obese Adults? A Review of the Literature. Preventive Medicine 1993  Cavadini, C., Siega-Riz, A.M., Popkin, B.M. “US Adolescent’s Food Intake Trends From 1965-1996.” Archives of Disease in Childhood, 2000  NSW Schools Physical Activity and Nutrition Survey (SPANS) 2004  Tracy L. Tylka, et al, The Weight-Inclusive versus Weight-Normative Approach to Health: Evaluating the Evidence for Prioritizing Well-Being over Weight Loss, Journal of Obesity, 2014  Storey ML, Forshee RA, Weaver AR, Sansalone WR, Demographic and Lifestyle factors associated with body mass index among children and adolescents, International Journal of Food Sciences and Nutrition, 2003  Simmons D., McKenzie, A., Eaton, S., et al, Choice and availability of takeaway and restaurant food is not related to the prevalence of adult obesity in rural communities in Australia. International Journal of Obesity 2005  De Onis, M. & Blossner, M. Prevalence and trends of overweight among preschool children in developing countries. American Journal of Clinical Nutrition, 2000  O’Dea J. The New Self-Esteem Approach for the Prevention of Body Image and Eating Problems in Children and Adolescents. Healthy Weight Journal 2002  Luepker RV, Perry CL, McKinlay SM, et al. Outcomes of a field trial to improve children’s dietary patterns and physical activity. The Child and Adolescent Trial
for Cardiovascular Health. CATCH collaborative group. Journal of the American Medical Association, 1996  Ritchie L, Ivey S, Masch M, et al. Pediatric Overweight: A Review of The Literature. California Center of Weight and Health College of Natural Resources, University of California –Berkeley, June 2001  Birch LL. et al. The variability of young children’s energy intake. NEJM 1991; Drucker RR. et al. Can mothers influence their child’s eating behavior? J Developmental Behavior Pediatrics 1999; Fischer JO, Birch LL. Restricting access to foods and children’s eating. Appetite, 1999  Birch, L.L., Johnson, S.L., Fisher, J.O. Children’s Eating: The Development of Food-Acceptance Patterns. Young Children 50, no. 2, 1995  O’Dea, J, Abraham, S. Knowledge, Beliefs, Attitudes and Behaviours related to weight control, eating disorders and body image in Australian trainee home economics and physical education teachers. Journal of Nutrition Education 2001  Tomiyama, A.J., Ahlstrom, B., & Mann, T., Long-term effects of dieting: Is weight loss related to health? Social and Personality Psychology Compass, 2013  L. Bacon, L. Aphramor, Weight Science: Evaluating the Evidence for a Paradigm Shift, Nutrition Journal, 2011