Obesity Management.Care & specialists in New Zealand

Obesity is a chronic disease of excess body fat that impairs health. The standard clinical definition uses body mass index: overweight 25-29.9, class I obesity 30-34.9, class II 35-39.9, and class III ≥40 kg/m². Asian populations have lower thresholds (overweight ≥23, obesity ≥27.5) reflecting earlier cardiometabolic risk.

Obesity has multifactorial causes: 40-70% heritability of body weight, obesogenic environments (calorie-dense food, sedentary work, sleep loss), medications that promote weight gain (antipsychotics, insulin, corticosteroids), hormonal and metabolic disorders, chronic stress, and adverse childhood experiences. It is rarely simply a question of willpower.

Bariatric surgery delivers the largest sustained weight loss (25-35% at 1-2 years, durable at 5-10 years) and reduces all-cause mortality 30-50% over 15-20 years. Among medications, tirzepatide 15 mg weekly produces 20.9% mean weight loss at 72 weeks (SURMOUNT-1), and semaglutide 2.4 mg weekly produces 14.9% at 68 weeks (STEP-1).

Semaglutide is a GLP-1 receptor agonist. It slows gastric emptying, increases satiety through brainstem and hypothalamic GLP-1 receptors, and reduces food reward. The STEP-1 trial showed 14.9% mean weight loss at 68 weeks at the 2.4 mg weekly dose, with greatest losses in patients reaching target dose and continuing therapy.

Bariatric surgery is offered to adults with BMI ≥40, or ≥35 with weight-related comorbidity, and increasingly to those with BMI 30-35 and type 2 diabetes (2022 ASMBS/IFSO guideline). Candidates require medical and psychological evaluation, demonstrated engagement with multidisciplinary care, and willingness to commit to lifelong follow-up.

Obesity is a chronic relapsing disease rather than a curable one. Significant durable improvement (5-25% sustained weight loss with major reductions in obesity-related disease) is achievable with combined lifestyle, pharmacotherapy, and surgery. Stopping active treatment usually leads to weight regain, so management is lifelong.

BMI is a useful screening tool but not perfect. It cannot distinguish muscle from fat, may overestimate adiposity in muscular athletes, and underestimate cardiometabolic risk in Asian populations. Waist circumference, body composition, and assessment of obesity-related complications refine the diagnosis.

GLP-1 receptor agonists are generally well-tolerated. Common adverse effects are nausea, vomiting, diarrhea, constipation, and gallstones, mostly mild and improving with slow titration. Rare risks include pancreatitis and gastroparesis. They are contraindicated in personal or family history of medullary thyroid cancer or MEN2.

Weight regain is typical. The STEP-4 trial showed approximately two-thirds of lost weight was regained within a year of stopping semaglutide. Obesity is a chronic disease that responds to ongoing treatment; current evidence supports indefinite continuation of effective therapy when tolerated.

Sleeve gastrectomy produces 25-30% total body weight loss at 1-2 years, with durable ≥20% weight loss at 5-10 years in 60-70% of patients. Type 2 diabetes remission occurs in 30-50% at 5 years, and substantial improvements in hypertension, sleep apnea, and MASLD/NAFLD are typical.

Modern bariatric surgery in accredited centers has 30-day mortality of 0.1-0.3% and major complication rates of 3-5%, comparable to laparoscopic cholecystectomy. Long-term complications include nutritional deficiencies, dumping syndrome, and internal hernia (bypass), all manageable with appropriate follow-up.

Yes. The 2023 American Academy of Pediatrics guideline supports intensive health behavior and lifestyle treatment for children 6 and older, and offers pharmacotherapy (semaglutide, liraglutide) from age 12 and bariatric surgery for adolescents with severe obesity and comorbidity. Family-based programs are foundational.

No single diet is uniquely effective; adherence is the strongest predictor. Mediterranean, DASH, low-carbohydrate, plant-forward, and structured meal-replacement patterns all produce similar weight loss in head-to-head trials when calorie-controlled. Choose a sustainable pattern aligned with preferences and culture.

Sleep below 6 hours per night raises ghrelin (hunger), lowers leptin (satiety), increases late-evening eating, impairs glucose tolerance, and is associated with 25-50% higher obesity risk in adults. Improving sleep duration and quality is a core component of obesity treatment.

Exercise alone produces modest weight loss (typically 2-3 kg at 12 months) because energy expenditure is partially offset by increased hunger and reduced spontaneous activity. Combined with dietary change and behavioral support, however, exercise is critical for maintaining weight loss and preserving lean mass.

Yes. Common-variant heritability accounts for 40-70% of BMI variation. Rare monogenic forms (MC4R, LEPR, POMC, PCSK1, BDNF mutations) cause severe early-onset obesity and may respond to targeted therapies such as setmelanotide. Genetic testing is offered in early-onset severe obesity or syndromic features.

Yes, in many patients. The DiRECT trial showed 46% of patients with type 2 diabetes of less than 6 years duration achieved remission with a structured weight-loss program. Bariatric surgery produces durable diabetes remission in 30-60%. Tirzepatide and semaglutide both substantially improve glycemic control with weight loss.

Weight regain reflects biological defense of a higher fat-mass setpoint, including reduced resting metabolic rate, increased hunger hormones (ghrelin), and reduced satiety signals (leptin, PYY) for years after weight loss. Continued active treatment — lifestyle, pharmacotherapy, or surgical effects — counteracts these mechanisms.

Family history is the strongest non-modifiable risk factor. Children with two parents with obesity have an approximately 80% lifetime risk. This combines polygenic susceptibility, shared environment, and learned behaviors. Identifying family history early supports earlier intervention.

Severe (class III) obesity is BMI ≥40 kg/m², or ≥35 with weight-related comorbidity. Approximately 9.2% of US adults meet this threshold. Severe obesity carries the highest risk of cardiovascular disease, sleep apnea, MASLD/NAFLD, and obesity-related cancers, and is the strongest indication for bariatric surgery.

Yes. Chronic psychological stress elevates cortisol, alters reward and emotion regulation, and increases emotional and binge eating patterns. Adverse Childhood Experiences scores correlate strongly with adult obesity risk. Mental health support is a core component of comprehensive obesity treatment.