Obesity

Obesity is a complex, chronic, and relapsing disease characterized by an excessive accumulation of body fat (adiposity) to the extent that it may negatively affect your health. It is commonly defined and classified using the Body Mass Index (BMI), which is calculated as your weight in kilograms divided by the square of your height in meters (kg/m²). For the general adult population, the World Health Organization (WHO) classifies obesity as a BMI of 30.0 kg/m² or higher. Waist circumference is also an important measure, as it assesses central body fat, which is an independent predictor of health risks. For women, a waist circumference of 80 cm (31.5 in) or more indicates increased risk, and 88 cm (35 in) or more indicates high risk. Obesity is a multifactorial disease resulting from a complex interaction between genetic, environmental, behavioral, and metabolic factors. The fundamental cause is a long-term energy imbalance, where more calories are consumed than expended. This involves dysregulation of the central nervous system pathways that control appetite, satiety, and energy balance. Genetic predisposition plays a significant role, and modern environments often promote increased consumption of energy-dense foods while discouraging physical activity. Emerging evidence also suggests that the composition of the gut microbiome may influence how your body extracts energy from food and stores fat.

Symptoms

Breathlessness on exertion
Increased sweating
Snoring
Difficulty with physical activity
Joint and back pain, especially in knees, hips, and lower back
Fatigue and lethargy
Skin problems, such as rashes in skin folds (intertrigo) and dark, velvety patches of skin (acanthosis nigricans), which can be a sign of insulin resistance
Irregular menstrual periods or difficulty getting pregnant in women
Erectile dysfunction in men

Causes & Risk Factors

A long-term imbalance between the calories consumed and the calories expended
Complex interactions between genetic, environmental, behavioral, and metabolic factors
Dysregulation of brain pathways that control appetite, fullness, and energy balance (neurohormonal dysregulation)
Genetic predisposition, with over 100 gene variants linked to appetite, food cravings, and metabolic rate
Modern environments that encourage eating energy-dense foods and discourage physical activity ('obesogenic environments')
Emerging evidence suggests the gut microbiome (bacteria in the digestive system) may influence how your body extracts energy from food and stores fat
Dietary patterns high in energy-dense foods, sugary drinks, processed foods, and large portion sizes
Sedentary lifestyle and low levels of physical activity
Insufficient sleep or poor sleep quality
Certain medications, including some antidepressants, antipsychotics, corticosteroids, anticonvulsants, and diabetes medications like insulin and sulfonylureas
Lower income and education levels
Environmental factors like limited access to healthy foods ('food deserts') and few opportunities for physical activity
Chronic stress, which can lead to weight gain through hormonal changes and altered eating behaviors
Genetics, with a strong inherited component influencing appetite, metabolism, and body fat distribution
Increasing age, often due to a slower metabolism and changes in body composition
Sex, as women are more likely to have obesity than men, influenced by hormonal factors related to menopause and pregnancy
Certain racial and ethnic groups have a higher prevalence of obesity
Underlying medical conditions such as Cushing's syndrome, polycystic ovary syndrome (PCOS), and hypothyroidism

Diagnosis

Calculating Body Mass Index (BMI) using your weight and height. For adults, obesity is diagnosed with a BMI of 30.0 kg/m² or higher. For children and adolescents, it's a BMI at or above the 95th percentile for their age and sex.
Measuring waist circumference to assess central body fat, especially for adults with a BMI between 25.0 and 34.9 kg/m², as this can indicate increased health risks.
Reviewing your medical history, including past weight changes, eating habits, physical activity levels, existing health conditions, and medications that might cause weight gain.
A physical examination to measure height, weight, waist circumference, and blood pressure, and to look for signs of related health conditions.
Blood tests, which may include a lipid profile (cholesterol, triglycerides), blood sugar levels (fasting plasma glucose, HbA1c), liver function tests, and thyroid function tests to check for underlying causes or complications.

Treatment Options

Lifestyle Changes: This includes adopting a reduced-calorie diet focused on nutrient-dense foods and aiming for at least 150 minutes of moderate-intensity aerobic activity per week, along with muscle-strengthening activities.
Behavioral Therapy: Comprehensive programs that teach self-monitoring, goal setting, and strategies to manage eating behaviors and physical activity.
Medications: For some adults with a BMI of 30 kg/m² or higher, or a BMI of 27 kg/m² or higher with at least one weight-related health condition, medications may be considered alongside lifestyle changes. Examples include liraglutide, semaglutide, tirzepatide, orlistat, phentermine-topiramate, and naltrexone-bupropion.
Bariatric Surgery: This may be an option for adults with a BMI of 40 kg/m² or higher, or a BMI of 35.0–39.9 kg/m² if you also have a significant weight-related health condition (like type 2 diabetes or high blood pressure). In some cases, it may also be considered for individuals with a BMI of 30.0–34.9 kg/m² with uncontrolled type 2 diabetes. Common procedures include sleeve gastrectomy and Roux-en-Y gastric bypass.
Specialist Referral: You may be referred to a specialist weight management service, dietitian, psychologist, or physical therapist for comprehensive care.
Long-term Follow-up: Obesity is a chronic condition requiring ongoing monitoring of weight, blood pressure, and metabolic health, along with continued support for lifestyle changes.

Frequently Asked Questions

Is my BMI the only thing that matters for diagnosing obesity?

While Body Mass Index (BMI) is a primary tool for diagnosing obesity in adults (BMI of 30.0 kg/m² or higher) and children (BMI at or above the 95th percentile for age and sex), it's not the only factor. Your healthcare provider may also measure your waist circumference to assess central body fat, which is an independent predictor of health risks. They will also consider your overall health, medical history, and any existing health conditions.

Could a medical condition like my thyroid be causing my weight gain?

Yes, certain underlying medical conditions can contribute to weight gain. These include hypothyroidism (an underactive thyroid), Cushing's syndrome, and polycystic ovary syndrome (PCOS). Your doctor may perform tests, such as thyroid function tests, to rule out these conditions as a cause for your weight gain.

Are there specific foods I must avoid to lose weight?

While no single food must be completely avoided by everyone, a healthy diet for weight loss generally focuses on reducing calorie intake. This often means limiting energy-dense foods, sugary drinks, processed foods, and large portion sizes. Instead, emphasize nutrient-dense foods like fruits, vegetables, whole grains, and lean proteins. Your healthcare provider or a dietitian can help you create a personalized eating plan.

How much exercise do I really need to do to lose weight?

For weight management, guidelines recommend aiming for at least 150 minutes of moderate-intensity aerobic activity per week, along with muscle-strengthening activities on two or more days a week. More physical activity may be needed to maintain weight loss over time. It's important to find activities you enjoy and can sustain.

Why do I regain weight every time I stop a diet?

Weight regain is common after weight loss efforts because obesity is a chronic, relapsing disease. After losing weight, your body can undergo physiological changes, such as a decreased metabolic rate and increased levels of appetite-stimulating hormones, which can make it harder to keep the weight off. Long-term adherence to healthy behaviors and, in some cases, ongoing medical support are crucial for maintaining weight loss.

Are weight loss medications safe for long-term use?

Weight loss medications are generally considered for long-term use as an adjunct to lifestyle changes for individuals who meet specific criteria (BMI ≥ 30 kg/m², or BMI ≥ 27 kg/m² with a weight-related comorbidity). The safety and effectiveness of these medications for long-term use are evaluated in clinical trials. Your doctor will discuss the potential benefits and risks with you to determine if they are appropriate for your situation.

What are the side effects of the new weight loss injections like Wegovy or Zepbound?

The dossier mentions liraglutide (Saxenda), semaglutide (Wegovy), and tirzepatide (Zepbound) as approved medications. While specific side effects are not detailed in the dossier, these medications are GLP-1 receptor agonists (and GIP for tirzepatide). Like all medications, they have potential side effects, which your healthcare provider will discuss with you. It's important to review the specific drug information with your doctor.

Am I a candidate for weight loss surgery?

Bariatric surgery may be considered for adults with a Body Mass Index (BMI) of 40 kg/m² or higher, or a BMI of 35.0–39.9 kg/m² if you also have a significant weight-related health condition, such as type 2 diabetes or high blood pressure. In some cases, it may also be considered for individuals with a BMI of 30.0–34.9 kg/m² with uncontrolled type 2 diabetes. A specialist assessment is needed to determine if surgery is right for you.

What are the different types of bariatric surgery and their risks?

Common types of bariatric surgery include sleeve gastrectomy and Roux-en-Y gastric bypass. Adjustable gastric banding is less common now. While the dossier lists these procedures, it does not detail their specific risks. Your surgeon will explain the potential benefits and risks of each procedure during your consultation.

Will I have to be on a special diet for the rest of my life after surgery?

After bariatric surgery, you will need to follow specific dietary guidelines, often for the rest of your life, to ensure proper nutrition, prevent complications, and maintain weight loss. This typically involves smaller portion sizes, specific food choices, and vitamin supplementation. Your healthcare team, including a dietitian, will provide detailed guidance.

How does obesity affect my chances of getting pregnant?

Obesity can affect your chances of getting pregnant by contributing to irregular menstrual periods and infertility in women. It can also be associated with conditions like polycystic ovary syndrome (PCOS), which impacts fertility.

What are the risks of being obese during pregnancy for me and my baby?

For the mother, obesity during pregnancy increases the risk of gestational diabetes, pre-eclampsia (high blood pressure during pregnancy), blood clots, needing labor induction or a C-section, postpartum hemorrhage, and wound infections. For the baby, there's an increased risk of miscarriage, stillbirth, certain birth defects (especially neural tube defects), being born larger than average (macrosomia), and a higher chance of developing childhood obesity later in life.

How much weight should I gain during pregnancy if I already have obesity?

The dossier does not specify exact weight gain recommendations for pregnant women with obesity. However, it is important to discuss appropriate weight gain goals with your healthcare provider, as these are individualized based on your starting weight and overall health.

Is it safe to try to lose weight while I am pregnant?

The dossier does not directly address the safety of weight loss during pregnancy. Generally, weight loss is not recommended during pregnancy. Instead, the focus is on healthy weight gain and managing any obesity-related complications. It is crucial to discuss any weight concerns with your healthcare provider during pregnancy.

How can I prevent my child from developing obesity?

You can help prevent your child from developing obesity by promoting healthy dietary patterns from a young age, encouraging regular physical activity, ensuring they get adequate sleep, and encouraging breastfeeding if possible. Creating a supportive home environment that prioritizes healthy choices is also key. Regular screening for overweight and obesity in children and adolescents, starting at age 2, is also recommended.

Is my child's weight a problem, or is it just 'baby fat'?

For children and adolescents, obesity is defined using BMI-for-age growth charts. A BMI at or above the 95th percentile for their age and sex indicates obesity. It's important to consult with your child's pediatrician, who can assess their growth chart and determine if their weight is a concern, rather than assuming it's just 'baby fat'.

What is the best way to talk to my teenager about their weight?

The dossier does not provide specific guidance on how to talk to teenagers about their weight. However, it emphasizes that obesity is a complex disease with psychosocial impacts like low self-esteem and stigma. Approaching the conversation with empathy, focusing on health and well-being rather than just weight, and involving healthcare professionals can be helpful.

Does my metabolism slow down as I get older?

Yes, the risk of obesity increases with age, often due to a metabolic slowdown and changes in body composition. This is a non-modifiable risk factor for obesity.

Can stress and poor sleep really cause weight gain?

Yes, chronic stress can lead to weight gain through hormonal changes (like increased cortisol) and changes in eating behaviors. Insufficient sleep or poor sleep quality are also identified as modifiable risk factors for obesity.

If I lose weight, will my other health problems like diabetes and high blood pressure go away?

Losing even a modest amount of weight (5-10% of initial body weight) can significantly improve conditions like glycemic control (blood sugar), blood pressure, and cholesterol levels, and reduce the risk of developing type 2 diabetes. With substantial weight loss, especially from bariatric surgery, many comorbidities, particularly type 2 diabetes, can go into remission. However, long-term management is often still needed.

What is the difference between 'overweight' and 'obesity'?

Both overweight and obesity are defined using Body Mass Index (BMI). For adults, overweight is a BMI between 25.0 and 29.9 kg/m², while obesity is a BMI of 30.0 kg/m² or higher. For children and adolescents, overweight is a BMI at or above the 85th percentile and below the 95th percentile for their age and sex, while obesity is a BMI at or above the 95th percentile.