Obesity and Type 2 Diabetes

Issues of Concern

The lifetime risk of developing diabetes in men aged 18 or older increases from 7% to 70% as the body mass index (BMI) increases from less than 18.5 kg/m² to over 35 kg/m². In women, the risk increases from 12% to 74% across the same BMI values.[3] Given this strong association, diabetes screening is recommended for all patients with obesity. Managing obesity is crucial for both the prevention and treatment of T2D. Weight loss leads to a significant reduction in the incidence of diabetes in at-risk populations. In a study, lifestyle modifications, including modest weight reduction (5%-10% of baseline weight) and at least 150 minutes of physical activity per week, led to over a 50% reduction in the incidence of diabetes.[4] 

Similarly, bariatric surgery has been associated with a 5-fold reduction in T2D incidence over 7 years.[5] Weight loss is also effective in managing T2D. Glycemic control improves proportionally with weight loss, sometimes leading to remission.[6] Treatment of T2D begins with lifestyle management, followed by pharmacological therapy and surgery when necessary.

BMI is the most commonly used metric to assess body weight, and it is calculated by dividing a patient’s weight in kilograms by the square of their height in meters (kg/m²). BMI is used to classify individuals into the following categories:

• Underweight: <18.5 kg/m²
• Healthy weight: 18.5 to 24.9 kg/m² (18.5-22.9 kg/m² for Asian populations)
• Overweight: 25 to 29.9 kg/m² (23-27.4 kg/m² for Asian populations)
• Obese, class 1: 30 to 34.9 kg/m² (27.5-32.4 kg/m² for Asian populations)
• Obese, class 2: 35 to 39.9 kg/m² (32.5-37.4 kg/m² for Asian population)
• Obese, class 3: ≥40 kg/m² (≥37.5 kg/m² for Asian populations)

The upper BMI value in each category is lower for individuals of Asian descent due to their higher body fat percentage and increased risk of T2D at lower BMI levels. Many international organizations have adopted these adjusted ranges to more accurately define obesity in Asian populations.[7]

Lifestyle Management

Obesity is a chronic medical condition and a known risk factor for the development of T2D. In patients diagnosed with overweight or obesity and T2D, treatment should begin with intensive lifestyle modifications, which include: 

• Self-management education for diabetes
• Nutritional counseling
• Increasing physical activity
• Psychosocial care, when indicated
• Smoking cessation for smokers [8]

Patient self-management education fosters a deeper understanding of coexisting chronic conditions and enhances knowledge about self-monitoring and adherence to medical treatment. Patient education begins at the time of diabetes diagnosis, continues annually, and is provided as needed when complications arise.[9] Interprofessional healthcare providers, including nurses, registered dietitians, primary care providers, and specialists, all play essential roles in patient education. Effective teaching methods include motivational interviewing, the use of visual aids, distributing handouts, and utilizing electronic resources to enhance learning.

The goal of lifestyle modification is to achieve at least a 5% weight loss, which is necessary to obtain meaningful health benefits.[10] The Look AHEAD trial offers extensive data on the impact of intensive lifestyle intervention (ILI), demonstrating sustained weight loss greater than 5% in over half of participants, with 27% achieving more than 10% weight loss at 8 years.[11] 

Participants in the ILI group required fewer medications for diabetes, hypertension, and lipid management. A daily calorie deficit of 500 to 750 kcal is generally recommended to achieve weight loss. Typically, this results in a daily calorie goal of 1200 to 1500 kcal/d for women and 1500 to 1800 kcal/d for men. Meal replacement plans may help some individuals achieve a targeted calorie deficit, but they are generally not sustainable for long-term use. More sustainable and effective dietary approaches include the DASH (Dietary Approaches to Stop Hypertension) diet and the Mediterranean diet.[12][13] 

Among intermittent fasting approaches, modified alternate-day fasting and the 5:2 diet are the only ones shown to produce statistically significant weight loss exceeding 5%.[14] 

The chosen diet should be tailored to the patient's cultural and dietary patterns, food availability, and other factors such as hunger and access to healthy foods. Counseling sessions for nutrition, physical activity, and behavioral goals aimed at achieving weight loss should be available to all patients. Standard intensive ILI includes more than 16 sessions over 6 months, with monthly follow-ups for those who achieve target weight loss after 1 year. However, this level of ILI may not be easily accessible or financially feasible in primary care settings. 

Individuals with T2D and obesity should be encouraged to gradually increase their physical activity. Most professional guidelines recommend at least 150 minutes of moderate-intensity exercise per week. The optimal plan combines aerobic exercise with 2 to 3 resistance training sessions weekly. Exercising daily or avoiding more than 2 consecutive days without activity helps reduce insulin resistance.[15]

Regular screening for mood disorders and other psychosocial factors associated with diabetes and obesity is essential.[16][17] Addressing coexisting mental health conditions can enhance treatment adherence and improve outcomes in patients with obesity and T2D.

Adolescents and adults with obesity and diabetes should be screened for tobacco use, including electronic cigarettes. Smoking is associated with an increased risk of developing diabetes, possibly by increasing insulin resistance.[18] Clinicians should offer counseling and consider appropriate pharmacological interventions to support smoking cessation.

Medical Evaluation and Treatment

If lifestyle modifications do not result in adequate weight loss, clinicians should evaluate the patient’s medical history for contributing factors. This includes reviewing the use of obesogenic medications, such as thiazolidinediones, beta-blockers, sulfonylureas, insulin, antipsychotics, antidepressants, steroids, and gabapentin (see Image. A Schematic Overview of Treatment Options for Type 2 Diabetes and Obesity). 

Pharmacotherapy is recommended as an adjunct to ILI for patients with a BMI over 30 kg/m² (>25 kg/m² in Asians) or over 27 kg/m² (>23 kg/m² in Asians) if they have a weight-related complication such as hypertension, dyslipidemia, T2D, or sleep apnea.[19] 

After initiating therapy, clinicians should closely monitor patients for the efficacy of the medication and potential adverse effects. Early responders who lose at least 5% of their body weight within the first 12 weeks are more likely to achieve sustained and significant weight loss. Most weight loss medications are intended for long-term use. Although medical therapy for weight loss was initially studied for short-term use, evidence supporting long-term use has emerged over the past two decades. However, the United States Food and Drug Administration (FDA) has approved phentermine only for short-term use (<12 weeks) due to concerns about potential abuse.

FDA-Approved Medications for Long-Term Weight Management in Obesity and Type 2 Diabetes

Phentermine-topiramate, extended-release

This combination medication was approved by the FDA in 2012 and demonstrated an average weight loss of 10% in the SEQUEL trial, compared to less than 2% in the placebo arm.[20] The drug is effective for patients ranging from overweight to class 3 obesity, including those with a BMI of over 45 kg/m². The initial dose consists of 3.75 mg of phentermine combined with 23 mg of extended-release (ER) topiramate (3.75 mg/23 mg). The dosage can be titrated up to 15 mg/92 mg in 2-week intervals as tolerated.

Common adverse effects include insomnia, increased blood pressure, dry mouth, and paresthesias. This medication should not be used concurrently with monoamine oxidase inhibitors. Because phentermine-topiramate is associated with an increased risk of congenital malformations such as cleft lip or cleft palate, clinicians must confirm that women of childbearing age are not pregnant and are using effective contraception before prescribing.

Liraglutide, semaglutide, and tirzepatide 

Liraglutide and semaglutide are glucagon-like peptide-1 (GLP-1) receptor agonists, whereas tirzepatide is a dual glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 receptor agonist. Although these agents were initially approved for the treatment of T2D, they have also demonstrated significant benefits for weight loss. They promote weight reduction through multiple mechanisms, including enhanced insulin secretion, improved insulin sensitivity, suppression of glucagon, delayed gastric emptying, and increased satiety via central nervous system effects. However, high cost and limited insurance coverage may restrict access to these medications.

Liraglutide, as studied in the SCALE trial, resulted in approximately 5% additional weight loss compared to the placebo.[21] The dosing starts at 0.6 mg daily, administered subcutaneously (SC), and is titrated weekly to a maximum of 3 mg daily SC. The most common adverse effects are gastrointestinal disturbances and nausea.

The STEP clinical trial evaluated semaglutide and demonstrated a 15% to 16% weight loss by week 68.[22] This medication achieves more substantial weight loss compared to semaglutide. The initial dose is 0.25 mg, administered SC once weekly, with gradual increases every 4 weeks up to a maximum dose of 2.4 mg weekly.

The SURMOUNT-2 trial evaluated tirzepatide for weight loss in individuals with T2D and a BMI of over 30 kg/m² or over 27 kg/m² with weight-related comorbidities, including T2D.[23] Tirzepatide’s dual mechanism—combining GLP-1 receptor agonism with glucose-dependent GIP activity—provided greater efficacy in glycemic control and weight reduction compared to GLP-1 receptor agonists alone. Approximately 20% weight loss was observed with the maximum 15 mg per week SC dose.

In the Phase III SURPASS trials, once-weekly SC tirzepatide, administered as monotherapy or as add-on therapy to oral glucose-lowering agents and insulin, demonstrated superiority over GLP-1 receptor agonists dulaglutide (0.75 mg) and semaglutide (1 mg).[24] The SURMOUNT-5 trial showed that among participants with obesity but without diabetes, tirzepatide also achieved significantly greater weight loss compared to semaglutide.[25] 

Naltrexone-bupropion sustained release 

This combination reduces food intake and promotes weight loss through multiple mechanisms. Naltrexone is an opioid antagonist, and bupropion is an antidepressant. The medication must be titrated gradually to minimize intolerance. The starting dose for naltrexone/bupropion is 1 tablet of 8 mg/90 mg daily, which may be increased to 2 tablets of 16 mg/180 mg twice daily as tolerated. This therapy is contraindicated in patients with uncontrolled hypertension, seizure disorders, or those receiving long-term opioid therapy.[26]

Orlistat

Orlistat is a pancreatic lipase inhibitor that prevents the absorption of fat. The medication is administered as a 60-mg tablet, taken 3 times daily with meals. The XENDOS trial demonstrated that treatment with orlistat resulted in approximately 5% weight loss.[27] Common adverse events include flatulence, abdominal pain, and fecal urgency, which can limit the usefulness or tolerability of this medication. Orlistat can also cause malabsorption of fat-soluble vitamins and increase the risk of cholelithiasis and nephrolithiasis.

Surgical Treatment

Surgical obesity treatment is indicated in patients with suboptimal weight loss or uncontrolled hyperglycemia. Surgery is recommended for patients with a BMI of over 40 kg/m², or a BMI between 35 and 39.9 kg/m² accompanied by hyperglycemia, weight-related comorbidities, or difficulty achieving sustainable weight loss. The Second Diabetes Surgery Summit reviewed evidence supporting surgery for patients with a BMI of 30 to 34.9 kg/m².

Metabolic and bariatric surgery is a safe and effective treatment option and should be considered in diabetic patients with a BMI of 30 to 34.9 kg/m² who exhibit uncontrolled hyperglycemia despite optimal medical therapy. Several surgical options are available for managing obesity, with the most common procedures including Roux-en-Y gastric bypass (RYGB), vertical sleeve gastrectomy (VSG), laparoscopic adjustable gastric banding (LAGB), and biliopancreatic diversion with duodenal switch (BPD).[2] 

RYGB and VSG are the most frequently used techniques as they have better long-term outcomes and safety data. BPD is effective, but is associated with increased complications. LAGB is the safest procedure but carries the highest risk of requiring revision and re-intervention. 

Surgery achieves beneficial outcomes by altering gastrointestinal anatomy to induce early satiety, reduce the absorptive surface area, and modulate hormones involved in glucose homeostasis.[28] Surgery also has a positive impact on intestinal glucose metabolism, and it alters pancreatic islet hormone activity, nutrient sensing, and bile acid metabolism.[29][30][31] 

RYGB has been shown in multiple human trials to enhance insulin sensitivity. Furthermore, it increases adiponectin levels (an insulin-sensitizing hormone) and muscle insulin receptors, promoting muscle fatty acid metabolism, which in turn reduces lipid accumulation in muscle and liver, and improves insulin sensitivity.[28] Another study demonstrated that RYGB increases insulin secretion through both glucose-dependent and glucose-independent mechanisms.[29] Due to its significant metabolic effects, bariatric surgery is often referred to as metabolic surgery.

Extensive data support the role of bariatric procedures in controlling and, in many cases, preventing T2D.[32][33][34][35][36] Although most randomized controlled trials comparing surgical treatments with ILI have follow-up periods of 1 to 2 years, some have extended to 5 years.[37] The surgical group experienced an average reduction in hemoglobin A1c (HbA1c) of approximately 2%, compared to 0.5% in the conventional treatment group. Most surgical patients achieved an HbA1c of about 6%. Remission of T2D—defined as a nondiabetic HbA1c without medication—was also achieved in the majority. Sustained remission has been reported in 30% to 60% of patients across multiple studies with follow-up periods ranging from 1 to 5 years. However, the benefits may decline over time, particularly in patients with poor preoperative glycemic control, longer diabetes duration, or those who use insulin.[38] 

Relapse of T2D occurred in 35% to 50% of patients. In the same study, RYGB was associated with a median disease-free period of 8.3 years. Surgical treatment improves glycemic control and clinical outcomes, even when remission is not achieved. One observational study with a 10- to 20-year follow-up reported significantly fewer complications and higher remission rates in the surgical group.[39] 

RYGB and BPD result in the most significant reductions in HbA1c and BMI. Multiple studies have evaluated patients with a BMI of 30 to 35 kg/m² and uncontrolled T2D, consistently showing improved HbA1c levels and higher remission rates in patients following surgery.[35][40][41][34] LAGB has demonstrated even better outcomes in patients with T2D and a BMI of 25 to 30 kg/m².[42]

Researchers have examined the economic impact of bariatric procedures on patients with T2D. The cost per quality-adjusted life-year (QALY) for metabolic surgery typically ranges from $3200 to $6300, which is well below the $50,000 estimate for nonsurgical care.[2] A 15-year follow-up of the Swedish Obese Subjects (SOS) study found no significant difference in total healthcare costs between patients with obesity and T2D treated conventionally or with bariatric surgery.[43] 

Metabolic surgery has become significantly safer and more effective over the past 2 decades, although outcomes are highly dependent on the surgeon's expertise. Mortality rates are low, ranging from 0.1% to 0.5%. Nonetheless, surgeons must thoroughly discuss potential risks and complications as part of informed consent and shared decision-making.[2][44] Reoperation and readmission rates are 2.5% and 5.1% for RYGB, 0.6% and 5.5% for VSG, and 0.6% and 2% for LAGB, respectively.[45] 

Long-term follow-up demonstrates that LAGB has the highest rates of removal or revision. Although VSG is a relatively new procedure, its popularity has increased as surgical experience has improved. BPD is the most complex procedure and carries higher risks of mortality, morbidity, and complications. Clinicians should educate all bariatric surgery patients about the potential for postoperative nutritional deficiencies, such as iron deficiency anemia, hypoglycemia, and bone demineralization, and closely monitor them for both short-term and long-term complications.

Clinical Significance

Many healthcare quality metrics assess the effectiveness of diabetes prevention and treatment. Obesity is a major risk factor for T2D, influencing both its development and severity. Early screening of patients with obesity, combined with intensive treatment, can lead to long-term improvement or remission. Strict diabetes control reduces complications such as ketoacidosis, diabetic ulcers, amputations, soft tissue infections, and osteomyelitis. Additionally, aggressive management of HbA1c lowers the risk of coronary artery disease and chronic kidney disease.

Enhancing Healthcare Team Outcomes

Diabetes is a chronic, disabling illness, and the ongoing obesity epidemic is driving its increasing incidence. Treating obesity is crucial for both preventing and managing T2D, with successful outcomes relying on coordinated, interprofessional care among healthcare providers. Early identification of patients with obesity in primary care is a crucial first step in achieving optimal clinical outcomes.

Nurses are often the first point of contact, and they should accurately measure height and weight, calculate the BMI, and document these measurements consistently. Nursing staff should also review dietary habits and physical activity at baseline and during each follow-up visit. Patients with an elevated BMI are at an increased risk for T2D and should be informed of their BMI category during treatment discussions. Clinicians should support patients in setting individualized weight loss goals, ideally aiming for at least a 10% reduction in body weight to achieve meaningful metabolic improvements. Intensive lifestyle interventions and pharmacotherapy should be initiated in accordance with current clinical guidelines.

Suboptimal glycemic control should be evaluated and managed at every visit. Inadequate weight loss (defined as less than 10%) and ongoing hyperglycemia should prompt referral to an obesity medicine specialist or bariatric surgeon for further evaluation and treatment. Physicians, surgeons, and other clinicians often collaborate in multidisciplinary weight loss programs. Obesity medicine physicians help patients in achieving the target weights needed for surgical eligibility. They also play a critical role postoperatively by identifying complications and supporting healthy behaviors to maintain ongoing weight loss. Although many patients are ineligible for metabolic surgery due to operative risks from advanced cardiac or pulmonary disease, obesity medicine teams can still achieve positive outcomes for this population.

Registered dietitians, nutritionists, and therapists are essential members of the healthcare team, providing regular sessions to support optimal nutrition and physical activity. These healthcare teams may be led by trained professionals such as dietitians, therapists, nurses, physicians, or surgeons. Endocrinology consultations can offer additional strategies for managing persistent hyperglycemia. High-risk patients may require preoperative assessments by cardiologists or pulmonologists, and procedures should be performed in centers with on-site cardiac and pulmonary critical care. Pharmacists play a vital role in adjusting medication dosages, particularly in the perioperative period, as many drugs require weight-based dosing modifications after surgery.

The anesthesia team conducts preoperative evaluations and manages anesthesia-related events during and after metabolic procedures. Physical therapists assist patients with muscle strengthening in the postoperative period. Given the common association between obesity and mental health conditions, such as anxiety, depression, and body image disorders, psychiatry or psychology consultations should be considered when indicated.

Obesity and type 2 diabetes are chronic, systemic conditions that require a coordinated interprofessional approach for effective prevention and management. Members of the interprofessional healthcare team should support patients during their evaluation and treatment, providing them with ample resources and guidance to help them make informed decisions and achieve the best possible clinical outcomes.

Nursing, Allied Health, and Interprofessional Team Interventions

Interprofessional interventions focus on identifying T2D in patients with obesity. Providers should be aware of medications that contribute to weight gain and consider appropriate alternatives. Nurses record BMI at each visit and notify the provider when the value exceeds 25 kg/m². Patients meeting this threshold are screened for T2D if they have not been previously tested. Primary care clinicians initiate lifestyle interventions for all patients with a BMI of 25 kg/m² or higher. Standard written instructions about diet and exercise are reviewed at each visit.

Clinicians assist patients in setting realistic, measurable weight loss goals, aiming for a BMI below 25 kg/m² or a 5% to 10% weight loss. A BMI over 30 kg/m² alerts providers to consider ILI and pharmacological treatments. Registered dietitians and nutritionists provide patients with knowledge to make informed, healthy dietary choices. Effective outcomes rely on an interprofessional approach with clear communication between primary care providers and endocrinologists. When ILI and pharmacotherapy do not achieve adequate diabetes control and weight loss, timely referral to bariatric and metabolic surgeons is crucial for optimal care.

Nursing, Allied Health, and Interprofessional Team Monitoring

Members of the interprofessional team caring for patients with diabetes and obesity monitor HbA1c, body weight, BMI, and lifestyle changes at every visit. Clinicians educate patients about potential medication adverse effects and adjust doses as needed, whereas pharmacists reinforce this counseling and manage medication reconciliation.

After metabolic surgery, patients require close monitoring by the healthcare team. Although surgical patients require fewer medications because of improved metabolic parameters, there is a higher risk of hypoglycemia. Nurses identify and document complications such as wound dehiscence, perforation, and signs of infection, and promptly alert healthcare providers. Clinicians, dietitians, and nutritionists assess for signs of metabolic derangements, including vitamin and mineral deficiencies or malabsorption syndromes. Avoiding continuous use of nonsteroidal anti-inflammatory drugs during the first month helps prevent erosion of anastomosis sites. Internal quality metrics evaluate remission rates, procedural safety, postoperative recovery, and long-term outcomes after surgery.

Obesity increases the risk of T2D, cardiovascular disease, and numerous other chronic health conditions. Effective healthcare teams routinely screen for obesity and diabetes, using BMI to assess the severity of obesity. ILI and pharmacological therapy aim for at least 10% weight loss. Patients who do not achieve adequate weight loss or glycemic control despite optimal medical treatment should be referred for bariatric surgery. Over the past two decades, these procedures have become increasingly safe and effective. Continued postoperative monitoring by the interprofessional team is essential for early detection of complications and sustained clinical improvement.