Definition

Weight gain is defined as an increase in body weight over time, typically measured by an increase in body mass index (BMI) or overall body weight. Clinically significant weight gain is often considered as an increase of 5% or more of body weight over a period of 6-12 months.

Etiology

Nutrition

• Excessive caloric intake
• High-fat, high-sugar diet
• Increased portion sizes
• Frequent consumption of processed foods
• Liquid calories (e.g., sugary drinks, alcohol)

Endocrine

• Hypothyroidism: Reduced metabolism due to low thyroid hormone levels
• Cushing’s syndrome: Excess cortisol production
• Polycystic ovary syndrome (PCOS): Hormonal imbalance affecting metabolism
• Insulin resistance and hyperinsulinemia

Medication

• Antipsychotics (e.g., olanzapine, risperidone)
• Antidepressants (e.g., certain SSRIs, tricyclic antidepressants)
• Corticosteroids (e.g., prednisone)
• Beta-blockers
• Some diabetes medications (e.g., sulfonylureas, thiazolidinediones)
• Hormonal contraceptives

Mental Health

• Depression: Can lead to increased appetite and reduced physical activity
• Anxiety disorders: May result in emotional eating
• Binge eating disorder
• Seasonal affective disorder (SAD)

Genetic Conditions

• Prader-Willi syndrome
• Bardet-Biedl syndrome
• Down syndrome
• Leptin deficiency or leptin receptor mutations
• Melanocortin 4 receptor (MC4R) mutations

Other – Sleep Apnea

• Obstructive sleep apnea (OSA): Associated with disrupted sleep patterns and hormonal imbalances
• Insufficient sleep: Can lead to increased appetite and cravings for high-calorie foods

Diagnostic Approach

1. Comprehensive medical history

• Dietary habits
• Physical activity level
• Medication review
• Family history of obesity and related conditions

1. Physical examination

• Height and weight measurements
• BMI calculation
• Waist circumference
• Blood pressure
• Signs of endocrine disorders (e.g., thyroid enlargement, acanthosis nigricans)

1. Laboratory tests

• Complete blood count (CBC)
• Lipid profile
• Fasting glucose and HbA1c
• Thyroid function tests (TSH, free T4)
• Cortisol levels (if Cushing’s syndrome is suspected)
• Liver function tests

1. Endocrine evaluation

• Insulin levels
• Sex hormone levels (for suspected PCOS)
• Growth hormone and IGF-1 (if growth hormone deficiency is suspected)

1. Sleep study

• Polysomnography for suspected sleep apnea

1. Psychological assessment

• Screening for depression, anxiety, and eating disorders

1. Genetic testing

• Consider for suspected genetic syndromes or early-onset severe obesity

1. Imaging studies

• Abdominal ultrasound or CT scan (if non-alcoholic fatty liver disease is suspected)
• MRI of the pituitary (if Cushing’s disease is suspected)

1. Nutritional assessment

• Detailed dietary recall
• Food diary analysis

1. Body composition analysis
   • Dual-energy X-ray absorptiometry (DXA) scan
   • Bioelectrical impedance analysis (BIA)

The diagnostic approach should be tailored to each patient’s specific presentation, risk factors, and clinical suspicion. Early identification of underlying causes can lead to more effective management strategies for weight gain.