In a recent review published on International Journal of Obesity, researchers reviewed recent developments in epidemiologic data on type 1 diabetes (T1D) and weight disorders. They explore the challenges scientists and clinicians face in studying and treating these associations. Their findings dispel many myths about T1D, most notably that the chronic condition only affects thin teenagers. Finally, this review presents recommendations for therapeutic interventions against T1D and guidelines for future research on the topic.
Study: The emergence of obesity in type 1 diabetes. Image credit: Monkey Business Images
Obesity and diabetes – a brief history
Weight-related disorders, the most common of which are overweight and obesity, present significant clinical and socioeconomic burdens worldwide. Over 1 billion people worldwide suffer from obesity, with the condition estimated to have claimed over 5 million lives in 2019 alone. Worryingly, changing trends in diet and physical activity are leading to significant increases in obesity rates, with the current prevalence of of obesity nearly three times that of 1975. Western countries are most affected by this negative trend, with reports highlighting that obesity rates in the United States (US) have seen a fourfold increase since 1980.
Compared to the much more common type 2 diabetes (T2D), type 1 diabetes (T1D) is a rare, usually genetic condition that affects between 3-10% of people with diabetes. It is thought to be an autoimmune disorder and is characterized by a reduced or complete inability of the pancreas to produce insulin, resulting in a toxic build-up of sugar in the patient’s bloodstream. Because its onset historically occurred in teenagers, the condition was called “juvenile” diabetes, but recent research has discovered that T1D can develop in people of any age group.
In the US, T1D is reported to affect 5.6% of all diabetic patients. A popular clinical perception has been that T1D only affects thin people, with overweight and obese people immune to the condition. Given this perception and the trend of increasing prevalence of overweight post-coronavirus-2019 (COVID-19), the prevalence of T1D was expected to decrease. However, recent research has debunked this view and found a positive feedback loop of association between overweight disorders and T1D. This leads to predictions that the prevalence of T1D will increase from the current 3.7 million to more than 17 million by 2040.
T1D remains the least studied form of diabetes, with research into the disease a fraction of that of T2D. Improving professional and public knowledge about the disease, its causative factors, and optimal management strategies will allow clinicians to better prepare for the coming increase in patients with T1D and improve the quality of life for all patients with this chronic condition. .
About the study
This review aims to clarify current knowledge about the relationship between T1D and obesity, summarize the factors that cause both conditions, and discuss the best evidence-informed management strategies for the treatment of T1D. The PubMed online scientific repository (MEDLINE) was searched for all publications investigating obesity, T1D, known contributors and determinants of risk, and interventions against both conditions from database inception to June 2023. More were identified of 120 papers for descriptive abstract and post-title discussion , abstract view and full-text view.
The reviewed literature was summarized into four main subcategories – 1. Multi-ethnic patterns of obesity in type 1 diabetes, 2. Distinct biopsychosocial factors contributing to increased obesity in type 1 diabetes, 3. Treatments for obesity in patients with type 1 diabetes and 4 Future guidelines for the management of obesity in type 1 diabetes.
Study findings
Contrary to previously thought, overweight and obesity are significantly positively associated with T1D. The research revealed that in adolescents aged between 16 and 19 years, each additional standard deviation (SD) from the mean body mass index (BMI) was associated with a 25% increased risk of developing T1DM. These findings have been validated by Mendelian randomization studies and genome-wide association studies (GWAS).
Encouragingly, these GWAS also clarified an unexpected finding—children with severe obesity (and thus a high risk of T1D) could drastically reduce their T1D risk by up to 22% for every 10% weight loss. This suggests a critical window of opportunity where weight management interventions before the onset of T1D could potentially prevent the development of the condition, directly improving the future of thousands or even millions of would-be diabetic patients.
This review highlights the significant confounding between metrics and methodologies used to measure overweight/obesity and T1D worldwide, as noted by SEARCH (US-based), Diabetes Patienten Verlaufsdokumentation (Europe-based) , Type 1 Diabetes (US-based), all of which found positive associations between obesity and T1DM, but with prevalence ranging from only 15.3% to 36% or more. Similarly, the SWEET (Europe, India and Canada) cohort documented a trend of 10 reduced childhood and adolescent obesity, whereas the Diabetes Control and Complications Trial (DCCT) found no such reductions. Finally, UK-based studies found no association between obesity and T1D, in contrast to the aforementioned cohorts.
“Future comparative studies should evaluate the applicability of different measures of adiposity in the phenotyping of obesity in T1D to ensure reliable epidemiological data.”
Recent decades have seen unprecedented increases in poor health behaviours, notably consumption of energy-dense foods (e.g. the Western diet) and a shift to highly sedentary lifestyles, especially following the COVID-19 pandemic and the associated “work- from home.’ These trends have defined the obesity (obesity-causing) landscape, which is now known to result from a combination of genetic, political, socioeconomic and cultural factors. Unfortunately, despite the fact that new risk factors are being discovered almost daily, most have not received due attention, both by clinicians and policy makers.
“First, there is still insufficient understanding of obesity in the pathogenesis of T1D, which may hinder effective prevention and treatment strategies. A difficult dilemma in achieving weight management goals. Third, health disparities in T1D lead to a wide variation in disability-adjusted life years (DALYs), with unexplained gaps.”
Specifically, T1D is characterized by the induction of β-cell inflammation. This condition is exacerbated by obesity due to its comorbidities, including lipotoxicity, mitochondrial dysfunction, glucotoxicity, adipose tissue damage, endocrine alterations, and recently described imbalances in gut microbial communities. The interaction between these factors produces synergistic effects far more pronounced than when taken individually. Current research fails to incorporate these effects into its predictions and intervention recommendations, often resulting in suboptimal outcomes. Future clinical research should consider the holistic effects of T1D and diabetes and aim to treat diseases of the body rather than focusing on one at the expense of the other.
An ideal example of this is exercise, the main non-clinical intervention in the treatment of obesity. While high-intensity exercise greatly promotes weight loss, subjecting a T1D patient to vigorous physical activity can sometimes do more harm than good because it increases hyperglycemia (high blood sugar), the main complication of T1D. If used as an intervention, exercise should be tailored to account for both obesity and T1D (eg, low-intensity walking versus high-intensity running).
“Innovations in insulin pumps, continuous glucose monitoring, and automated insulin devices with sensors help control glycemic levels in most forms of exercise and hold out the most optimistic hope for exercise safety.”
Likewise, dietary and nutritional interventions tailored to address obesity may sometimes worsen T1DM, resulting in increased pharmacotherapeutic interventions (insulin injections). Nutritional interventions must be fine-tuned on a patient-by-patient basis rather than a one-size-fits-all medical nutrition therapy (MNT) approach.
The use of pharmacological interventions should similarly be extensively tested before use. Incretin mimetics (receptor agonists that increase insulin release from the pancreas) should be used with caution as they may cause unexpected weight loss effects. The importance of patient education and adaptive care as a growing body of evidence suggests that patient-reported symptoms may closely resemble clinically diagnosed medical profiles and may be used as preliminary proxies for the latter.
“Finally, attention to health care disparity should intensify. Evolving technological innovations and the limited availability of off-label drugs are increasingly leaning toward a first-world-centered solution.”
A growing body of research highlights that socioeconomically disadvantaged communities and racial minorities are most affected by T1D and obesity, a phenomenon that is exacerbated by the fact that they are at increased risk for both conditions. Policymakers and pharmaceutical companies should ensure fair and cost-effective healthcare management for all patients, regardless of their wallet size.
conclusions
T1D has historically received much less clinical and scientific attention than its much more common counterpart T2D, resulting in many myths and misinformation about its prevalence, associated risk factors, and optimal treatment. Recent research has begun to dispel these myths, revealing that the prevalence of T1D is higher than previously thought and its incidence is expected to increase in the coming years. Contrary to previously assumed, T1D is not limited to thin individuals. In contrast, its associations with weight abnormalities are synergistic and profound. Future research, policy, and interventions must be patient-specific and tailored to address T1D, obesity, and their comorbidities simultaneously.
“At a systemic level, an aligned multi-stakeholder initiative is needed to ensure the real value of the global action plan on this T1D obesity burden.”
