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Study Misleads About Efficacy of Weight Loss Interventions in Children
New insights about how to make an intervention in children and adolescents with metabolic syndrome: diet, exercise vs. changes in body composition. A systematic review of RCT by Perez et al.
This series is part of the work I’m doing with Weight Inclusive Nutrition and Dietetics (WIND) to create a comprehensive response to the disastrous American Academy of Pediatrics (AAP) guidelines for higher-weight children. I’m part of the team that is analyzing the research that, the AAP claims, supports their recommendations, and I’ll be publishing my breakdowns here as well.
Today I’m looking into “New insights about how to make an intervention in children and adolescents with metabolic syndrome: diet, exercise vs. changes in body composition. A systematic review of RCT by Albert Pérez E, Mateu Olivares V, Martínez-Espinosa RM, Molina Vila MD, Reig García-Galbis M
This is a meta-analysis of nine small studies with significant heterogeneity, which is to say that the fact that the studies are set up so differently makes the choice to attempt a meta-analysis questionable. There is uncritical and unexplored conflation of correlation and causation between body size and cardiometabolic factors as well as between the impacts of behavior changes and body size changes on cardiometabolic factors. Their findings do not support their conclusion.
Here is the deeper dive. The paragraphs in italics are from the study, they may contain weight stigma and be triggering.
Their goal was to find what interventions created the largest change in body composition in patients 19 and younger with metabolic syndrome (MS).
They start by giving a definition of MS: “Metabolic syndrome, also known as “Insulin Resistance Syndrome”, can be defined as a series of physiological, biochemical and metabolic factors that increase the risk for cardiovascular disease and type 2 diabetes (T2DM). These factors include insulin resistance, T2DM or glucose intolerance, hypertension and central ob*sity”
They then admit that “MS in the pediatric population is difficult to define” and that adaptations from the juvenile population have been applied for years, leading to “excessive variety in diagnosis of MS” leading to an occurrence between 0.9% and 11.4% depending on what definition is used.
It should be noted that the inclusion of “ob*sity” in definitions of MS is questionable as, unlike every other factor, which has shared symptomology, “ob*sity” is simply a shared height-weight ratio. This also creates confusion in examining “treatment” since simply changing the height-weight ratio is assumed, often without evidence, to create health benefits.
They also acknowledge that “the current definition of ob*sity based on weight and height cannot accurately identify all causes of ob*sity-related risk of CVD (cardiovascular disease). People with a normal BMI (body mass index) and high content of BF (body fat) are at greater risk of metabolic disturbance, systemic inflammation and mortality. Thus, the metabolic alteration observed in individuals with normal weight metabolic ob*se can be only due to the increase of body adiposity not detected by the BMI”
False. Note here that they can only reach this conclusion by clinging to the concept of “ob*sity” through the use of correlation. Their statement fails to point out that many “ob*se” people do not have MS. But instead of noting that using a height/weight ratio isn’t appropriate for assessing risk, they label people with “normal” BMI and high body fat “normal weight metabolic ob*se” This is not scientific. The root of the problem is the made up concept of “ob*sity” propped up by the extremely problematic concept of BMI.
Their conclusion that metabolic alteration “can be only due to the increase of body adiposity not detected by the BMI” is not supported by the evidence. They do not offer a causal mechanism for this, only that they are correlated. In fact, it could be due to things like perception of weight stigma, weight cycling, or other factors.
In Table 4 they offer interventions for changing body composition. They cite position papers and guidelines, none of which shows any proof that the interventions suggested can create significant, long-term weight loss. They grade their own evidence as D-Level.
“Current evidence suggests that the intervention of physical exercise in adolescents with overweight and ob*sity improves body composition, changes body fat, and therefore could improve some cardio-metabolic factors”
Again, this shows author bias toward weight loss. In fact, the intervention of physical exercise is shown, in adults, to improve cardio-metabolic factors directly (ie: Gaesser & Angadi, 2021) The notion that physical exercise creates health benefits through weight loss is an assumption with no evidentiary basis.
“In the lifestyle interventions, the authors of these studies relate the changes in body weight with the cardio-metabolic results”
The study they cite to support this [Effectiveness of lifestyle interventions in child ob*sity: systematic review with meta-analysis Ho et al.] finds that lifestyle interventions can lead to improvements in cardio-metabolic outcomes and, at least short-term, weight loss. The studies they examine are short term but, more importantly, they DID NOT find that the weight loss actually caused the cardiometabolic outcomes, and thus they don’t know whether it was the weight loss or the behavior changes that preceded improved cardiometabolic outcomes.
“The most traditional dietary patterns, including the Mediterranean diet, are associated with better metabolic profiles”
Again, while the eating patterns themselves are correlated with better metabolic profiles, that may be a direct relationship and it would not be valid to assume that weight loss mediates that relationship.
In terms of pharmacotherapy, they admit that “The advantage of using medication in interventions for the management of weight loss in patients aged 2 to 18 years is not yet clear”
They offer four points to justify their review:
1. Due to the prevalence observed in children and adolescents with MS [17,18,19].
Again, they admit that they have no idea what this prevalence even is – just that it’s somewhere between 0.9% and 11.4% depending on what definition is being used.
2. The search for which dietary intervention and physical exercise obtains greater changes in body composition in children and adolescents with MS, as described by the overweight, ob*sity and T2DM guidelines [27,29,30].
Here they are assuming that weight change will lead to health changes, ignoring the possibility that health-supporting behaviors offer direct health benefits.
3. The relationship between the changes in body composition and cardio-metabolic factors [44,45].
Their analysis is not actually created to determine anything about this relationship. They have no way to determine whether any cardiometabolic factor changes are due to behavior changes or body composition changes.
4. Adhering to the WHO Global Action Plan in the reduction [1,2], which is focused on the factors related to the diagnosis of MS [3,4].1
Both studies they cite for this discuss the impact of lifestyle factors on MS, not the impact of body size changes.
For their meta-analysis, they started with 1,781 studies but were only able to include 9 of them (.51%)
The studies ranged from 3 to 18-months, meaning that none of them was long enough to capture the weight gain that is typically seen between 24 and 50 months.
All nine studies were quite small, including from 25 to only 150 participants. The total of all the studies was only 630 subjects.
Given the small number of RCTs and the significant heterogeneity in their design (different definitions of MS, different measurements of body size, different interventions, etc.) a meta-analysis is, again, a questionable strategy.
The study that showed the greatest change in body composition (de Mello M.T., de Piano A., Carnier J., Sanches P.D.L., Corrêa F.A., Tock L., Ernandes R.M.Y., Tufik S., Dâmaso A.R. Long-term effects of aerobic plus resistance training on the metabolic syndrome and adiponectinemia in ob*se adolescents) only included 30 total subjects (and only 15 in the intervention group) The study began with 43 participants but 13 dropped out. The study’s goal was to determine whether aerobic training (AT) and resistance training (RT) provided greater benefits on cardiometabolic health than aerobic training alone. While they measured body composition, they did not find (or claim to find) that the weight loss (rather than the behaviors that were the actual intervention) created the change. The study defines “long-term” as 1 year, despite the known tendency of weight to be regained in years 2-5, and the fact that nobody but study authors who are desperate to claim long-term efficacy of their intervention would define one year as long-term in human subjects. Their conclusion is that “These findings suggest a clinical role of AT+RT in the control of metabolic syndrome in pediatric populations”. They conclude nothing at all about body composition change.
“It has been demonstrated that the changes in body composition produce favorable changes in the metabolic illness risk factors in children, adolescents and adults71”
The single study they cite in no way supports this statement. The study (Impact of Weight Regain on Metabolic Disease Risk: A Review of Human Trials, Kroeger et al.) is a study of adults that begins by admitting that almost everyone regains the weight that they lost. The study seeks to determine the impact of weight regain, or lack thereof, on cardiometabolic changes. They make no distinction between the impacts of behaviors vs that of weight change in interventions or during weight regain (for example, when people begin regaining weight, do they then abandon their health-supporting behaviors since they assume they aren’t “doing any good” because they were told that the health benefits come not from behaviors but from body size changes?)
Practical Recommendations for the Design of Future Clinical Trials of Patients with Overweight, Ob*sity, T2DM and MS
Given the multitude of issues with study, I would argue that these authors are not capable of providing scientifically solid recommendations for future trials, and I think their recommendations prove me right. They are entirely based on the assumption that weight change will create cardiometabolic health changes, ignoring completely the possibility that the behavior changes that precede both the health changes and the (at least short-term) weight changes may be responsible for both, as was found for adults in this study.
Limitations and Strengths of the Systematic Review
They list one of the strengths as “The range of search dates of this systematic review, having found 1781 clinical trials from 2005–2017.”
I would say that this might be more of a strength if more than 9 of these trials would have actually been included in the meta-analysis.
They also list as a strength: “The trial has been carried out and overseen by professionals versed in dietary intervention and physical exercise for patients with overweight, ob*sity, and T2DM”
I would argue that this is a weakness. When all of the authors are coming from a myopic focus on the weight-centric paradigm, they fail to question their own biases and assumptions. For example, they consistently make the absolutely rudimentary mistake of assuming causation from correlation.
“It is proposed to follow the guidelines proposed for patients with overweight, ob*sity and T2DM (Table 3 and Table 4) and extrapolate these strategies as recommendations to the future clinical trials designed in patients with MS.”
This conclusion is not supported by their data. Nine studies with eighteen months or less of follow-up on less than 1,000 subjects of varying ages, diagnostic criteria, interventions, and intervention success measures, with no way to measure long-term harm and no comparison to weight-neutral interventions, do not justify a treatment recommendation of any kind.
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*Note on language: I use “fat” as a neutral descriptor as used by the fat activist community, I use “ob*se” and “overw*ight” to acknowledge that these are terms that were created to medicalize and pathologize fat bodies, with roots in racism and specifically anti-Blackness. Please read Sabrina Strings Fearing the Black Body – the Racial Origins of Fat Phobia and Da’Shaun Harrison Belly of the Beast: The Politics of Anti-Fatness as Anti-Blackness for more on this.