Obesity and Overweight: What Are the Real Health Risks?

What is Obesity and Overweight?

The global situation is alarming. It is worsening at every age level, including among children. Experts describe the rise of overweight and childhood obesity as nothing less than a true epidemic.

Being overweight significantly increases the probability of developing a wide range of serious medical conditions. If you are currently overweight or obese, you may already be at increased risk for:

• Type 2 diabetes
• Coronary artery disease and stroke
• Metabolic syndrome
• Certain types of cancer
• Sleep apnea
• Osteoarthritis
• Gallbladder disease
• Non-alcoholic fatty liver disease (NAFLD)
• Pregnancy complications

A landmark study by Imperial College London in collaboration with the WHO confirms this global trend, warning that at the current pace we will soon reach the paradoxical situation where more children are overweight than underweight worldwide.

The good news is that even modest weight loss produces measurable, meaningful health benefits. You can substantially reduce your risks by:

• Losing weight gradually and in a medically controlled manner
• Practicing regular physical activity
• Adopting a healthy, balanced diet as a daily lifestyle, rather than just a temporary measure

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Diagnosis

Modern diagnosis of overweight and obesity goes far beyond simply stepping on a scale. It involves a multidimensional assessment to evaluate the extent of excess body fat. More importantly, this process also examines the patient’s overall cardiometabolic risk profile.

Assessing Anthropometric Parameters

The first and most widely used tool is the Body Mass Index (BMI), calculated by dividing body weight (in kilograms) by height squared (in meters). According to the World Health Organization, BMI categories are defined as follows:

However, BMI has well-recognized limitations: it does not distinguish between lean muscle mass and body fat, and can therefore misclassify muscular individuals as overweight or miss excess adiposity in those with low muscle mass (so-called “normal-weight obesity”).

For this reason, physicians integrate BMI with a measurement of waist circumference. This is a key parameter for detecting visceral obesity, which refers to the accumulation of fat around internal abdominal organs. Visceral obesity carries the highest cardiovascular and metabolic risk. Clinically significant visceral obesity is generally defined as:

• Men: waist circumference > 94 cm (increased risk) or > 102 cm (substantially increased risk)
• Women: waist circumference > 80 cm (increased risk) or > 88 cm (substantially increased risk)

In advanced clinical settings, additional tools include:

• Bioelectrical impedance analysis (BIA): to accurately measure body composition (fat mass vs. lean mass).
• Waist-to-height ratio (WHtR): This measure is increasingly recognized as a more sensitive predictor of cardiometabolic risk than BMI alone. A WHtR above 0.5 is generally considered a risk threshold.

Screening Tests and Biomarkers

To complete the diagnostic picture and identify early complications, a set of targeted blood tests and clinical assessments is typically ordered:

• Glycemic profile: fasting blood glucose and glycated hemoglobin (HbA1c) to screen for prediabetes or type 2 diabetes
• Lipid profile: total cholesterol, LDL (“bad” cholesterol), HDL (“good” cholesterol), and triglycerides
• Liver function tests: liver enzyme levels (ALT, AST) to detect signs of non-alcoholic fatty liver disease
• Blood pressure measurement: to screen for hypertension, a frequent comorbidity
• Comprehensive lifestyle history: including sleep quality assessment, eating behavior patterns, physical activity levels, and screening for binge eating disorder or other eating disorders

This integrated evaluation is essential for tailoring a truly personalized therapeutic plan.

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Treatment and Management

The modern approach to treating obesity and overweight focuses not just on reducing weight as shown on the scale. Instead, its primary goal is long-term maintenance of health and prevention of complications. Treatment is inherently multidisciplinary and follows a stepwise structure.

Lifestyle Changes (Behavioral Therapy)

The foundation of every treatment strategy is a structured, sustainable change in daily habits. This does not mean following a short-term restrictive diet, but adopting a new, lasting lifestyle model.

• Personalized nutrition: A diet with reduced caloric density is recommended. The Mediterranean diet, which is rich in fiber from vegetables, fruit, and whole grains, as well as lean protein and healthy fats like olive oil, and low in added sugars and saturated fats, is supported by the strongest evidence base. The target is a sustainable caloric deficit leading to a gradual weight loss of 0.5 to 1 kg per week.
• Physical activity: Current guidelines (WHO, AHA) recommend at least 150–300 minutes of moderate-intensity aerobic activity per week, ideally combined with muscle-strengthening exercises at least twice per week. Exercise is essential for preserving lean muscle mass during weight loss, which in turn sustains a higher resting metabolic rate.
• Psychological support: Cognitive-behavioral therapy (CBT) addresses the emotional and psychological drivers of overeating, helps patients manage stress without turning to food, and prevents long-term relapse. This component is often underestimated but is critical for sustainable success.

Pharmacological Therapy

When lifestyle interventions alone are insufficient to achieve clinically meaningful health outcomes, a physician may prescribe adjunct pharmacological therapy. Recent years have seen significant advances in this field:

• GLP-1 receptor agonists (e.g., semaglutide, liraglutide): These drugs mimic the action of a naturally occurring gut hormone that promotes satiety, slows gastric emptying, and improves glycemic control. They represent a major breakthrough in obesity pharmacotherapy and have demonstrated significant weight loss outcomes in clinical trials.
• GIP/GLP-1 dual agonists (e.g., tirzepatide): A newer class showing even greater efficacy in weight reduction than GLP-1 agonists alone.
• Gastrointestinal lipase inhibitors (e.g., orlistat): Act by reducing the intestinal absorption of dietary fats. Less potent than GLP-1 agents, but may be appropriate in selected patients.

Important: All pharmacological treatments must be used exclusively under close medical supervision, as part of a comprehensive program that includes diet and exercise. These are not standalone solutions.

Bariatric and Metabolic Surgery

For patients with severe obesity (BMI ≥ 40) or BMI ≥ 35 with obesity-related comorbidities (such as type 2 diabetes, hypertension, or obstructive sleep apnea), bariatric surgery remains the most effective long-term intervention for achieving and maintaining significant weight loss.

Common procedures include:

• Sleeve gastrectomy: Removes approximately 80% of the stomach, creating a narrow “sleeve” that restricts food intake and alters appetite hormones
• Roux-en-Y gastric bypass: Reroutes the digestive tract to bypass most of the stomach and part of the small intestine, combining restriction with reduced nutrient absorption and profound hormonal changes

These procedures can induce complete remission of type 2 diabetes in a high proportion of patients. This often happens before significant weight loss has even occurred, highlighting the powerful metabolic effects that go beyond simple caloric restriction.

Complementary Approaches and Warnings

Some dietary supplements (such as soluble fiber, green tea extract, or conjugated linoleic acid) may offer modest ancillary benefits in appetite regulation or fat metabolism. However, their effects are marginal when not combined with a balanced diet and exercise program.

Caution: It is essential to avoid unregulated “miracle” weight loss products or extreme fad diets. Many are not scientifically validated, and some pose significant risks to liver and cardiovascular health. Always consult a physician before starting any supplement for weight management.

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Type 2 Diabetes

Type 2 diabetes is a chronic metabolic condition where blood glucose levels remain consistently high. This condition is called hyperglycemia. If left untreated or poorly controlled, it is a leading cause of:

• Coronary artery disease and heart failure
• Chronic kidney disease and dialysis dependency
• Lower-limb amputations
• Blindness (diabetic retinopathy)
• Peripheral neuropathy

Type 2 diabetes is the most prevalent form of diabetes in Western countries and is strongly associated with obesity and physical inactivity.

Diabetes and Overweight

More than 85% of people with type 2 diabetes are overweight or obese. Excess adipose tissue, particularly visceral or abdominal fat, secretes inflammatory cytokines and free fatty acids. These substances impair insulin signaling, resulting in insulin resistance, the fundamental mechanism behind type 2 diabetes.

The evidence is clear and encouraging. Losing as little as 5–7% of body weight, through diet and increased physical activity, can significantly prevent or delay the onset of type 2 diabetes in at-risk individuals. This finding comes from landmark prevention trials, including the Diabetes Prevention Program.

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Stroke and Coronary Artery Disease

A coronary artery disease (CAD) occurs when the arteries supplying blood to the heart become narrowed or blocked. This typically happens because of the buildup of fatty plaques, a process called atherosclerosis.

If you have CAD, you are at substantially increased risk for:

• Myocardial infarction (heart attack)
• Heart failure
• Angina pectoris (chest pain)
• Stroke

Overweight, Heart Attack, and Stroke

Excess body weight, particularly abdominal fat, increases the risk of cardiovascular disease through multiple mechanisms. Here’s how it happens:

• Promoting hypertension (high blood pressure)
• Worsening dyslipidemia (elevated LDL, low HDL, high triglycerides)
• Driving a state of chronic low-grade systemic inflammation that directly damages blood vessel walls and accelerates atherosclerotic plaque formation
• Promoting insulin resistance, which in turn damages the endothelium (the inner lining of blood vessels)

The clinical benefit of weight reduction is well established: losing just 5–10% of body weight can lead to significant, measurable reductions in blood pressure, cholesterol levels, and overall cardiovascular event risk.

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Metabolic Syndrome

Metabolic syndrome is a cluster of interrelated metabolic abnormalities that, when present together, dramatically increase the risk of cardiovascular disease, type 2 diabetes, and stroke.

A diagnosis of metabolic syndrome is made when a patient presents with three or more of the following five criteria:

Weight management and regular physical activity are the most powerful interventions for reversing metabolic syndrome. Smoking cessation is also critically important, as smoking exacerbates all components of this syndrome and exponentially amplifies cardiovascular risk.

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Cancer

Cancer arises when cells begin to grow and divide in an uncontrolled manner, potentially spreading (metastasizing) to distant organs. The relationship between obesity and cancer is increasingly well established.

Overweight and Cancer Risk

According to the International Agency for Research on Cancer (IARC) and major oncology bodies, overweight and obesity are associated with an increased risk of at least 13 types of cancer, including:

• Colorectal cancer
• Esophageal cancer (particularly adenocarcinoma)
• Kidney (renal cell) cancer
• Uterine (endometrial) cancer
• Breast cancer (particularly in postmenopausal women)
• Pancreatic cancer
• Gallbladder cancer
• Liver cancer

The biological mechanisms linking obesity to cancer include:

• Hormonal dysregulation: Adipose tissue produces and stores estrogens and other hormones that can stimulate the proliferation of hormone-sensitive cancer cells
• Chronic systemic inflammation: Inflammatory cytokines secreted by visceral fat create a pro-tumorigenic microenvironment
• Insulin resistance and elevated IGF-1: High insulin levels and elevated insulin-like growth factor 1 (IGF-1) act as growth signals for cancer cells
• Altered adipokine secretion: Imbalances in hormones such as leptin and adiponectin promote tumor growth and angiogenesis

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Pregnancy Complications

Overweight and obesity can negatively affect fertility and substantially increase the risk of complications during pregnancy, for both mother and baby:

• Gestational diabetes: Pregnancy-induced insulin resistance is significantly amplified by pre-existing overweight
• Preeclampsia: A potentially dangerous condition involving high blood pressure and organ damage during pregnancy
• Increased likelihood of cesarean delivery and associated surgical complications
• Neural tube defects and other fetal structural abnormalities
• Macrosomia (excessively large baby) and complications during labor
• Increased risk of stillbirth
• Higher rates of preterm birth

For anyone planning a pregnancy, achieving a body weight closer to the healthy range before conception is one of the most impactful steps to protect both maternal and infant health.

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Childhood Obesity

Childhood obesity is a growing global health concern, with a significant proportion of children classified as overweight or obese. This trend is deeply concerning because conditions previously considered adult diseases, such as hypertension, non-alcoholic fatty liver disease, and type 2 diabetes, are now appearing in children and adolescents.

Childhood obesity carries particularly serious long-term consequences: obese children are significantly more likely to remain obese as adults and to develop cardiometabolic diseases at a younger age.

The first 1,000 days of life, spanning from conception to age two, represent a critical window for programming lifelong metabolic health. Evidence suggests that this period has an outsized influence on future obesity risk.

Key preventive strategies for families include:

• Promoting and supporting breastfeeding is essential; breastfed infants experience lower rates of childhood obesity
• Balanced weaning and complementary feeding: Limiting added sugars, processed foods, and excessive portion sizes from early childhood
• Limiting screen time: Excessive sedentary screen use is independently associated with obesity risk
• Encouraging at least 60 minutes of active play per day for children and adolescents
• Family-based behavioral interventions: The entire family’s lifestyle patterns profoundly influence a child’s eating behaviors and activity levels

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Sleep Apnea

Obstructive sleep apnea (OSA) is a condition characterized by repeated, brief interruptions of breathing during sleep. Each apneic episode causes a drop in blood oxygen levels, activating the body’s stress response and fragmenting sleep architecture.

The consequences extend well beyond daytime sleepiness and fatigue:

• Increased cardiovascular risk: OSA is independently associated with hypertension, arrhythmias (including atrial fibrillation), heart failure, and stroke
• Worsening insulin resistance and metabolic dysfunction
• Impaired cognitive function, concentration, and driving safety

The link with overweight is direct and mechanical: excess fat deposited in the neck and around the upper airway narrows the pharyngeal space, predisposing it to collapse during sleep. Weight loss is often the most effective treatment for mild-to-moderate OSA, sometimes eliminating the need for continuous positive airway pressure (CPAP) therapy entirely.

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Osteoarthritis

Osteoarthritis is a degenerative joint disease characterized by the progressive breakdown of articular cartilage. This cartilage serves as the protective cushioning between bones. The result is pain, stiffness, swelling, and loss of joint function.

Overweight and obesity damage joints through two distinct mechanisms:

1. Mechanical loading: Every extra kilogram of body weight exerts approximately 4 kg of additional force on the knee joints during walking. This accelerates cartilage erosion, particularly in weight-bearing joints (knees, hips, ankles, and lumbar spine).
2. Inflammatory pathway: Adipose tissue is metabolically active and releases pro-inflammatory molecules, such as leptin, IL-6, and TNF-α. These molecules directly promote joint inflammation and cartilage degradation, regardless of mechanical load.

The therapeutic implications are powerful: losing even 5% of body weight significantly reduces knee pain, improves joint function, and may slow disease progression.

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Gallbladder Problems

Obesity is a major risk factor for the development of gallstones (cholelithiasis). The mechanism involves supersaturation of bile with cholesterol. Obese individuals secrete more cholesterol into bile; this excess cholesterol precipitates and crystallizes, forming stones.

Conversely, and this is important, very rapid weight loss itself can also trigger gallstone formation. When fat is mobilized too quickly, the liver secretes even more cholesterol into the bile while simultaneously reducing bile salt secretion, creating conditions highly favorable to stone formation.

For this reason, medical guidelines recommend a gradual weight loss of no more than approximately 1–1.5 kg per week. If rapid weight loss is medically necessary (such as pre-bariatric surgery), prophylactic treatment with ursodeoxycholic acid may be prescribed to reduce gallstone risk.

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Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD), also called “fatty liver”, is the liver-related expression of metabolic syndrome. It has become the leading cause of chronic liver disease in Western countries.

NAFLD exists on a spectrum:

1. Simple steatosis: Fat accumulation in liver cells without significant inflammation, which is generally benign
2. Non-alcoholic steatohepatitis (NASH): A condition involving fat accumulation, inflammation, and liver cell injury, it carries a significant risk of progression
3. Liver fibrosis and cirrhosis: Irreversible scarring of liver tissue
4. Liver failure or hepatocellular carcinoma: End-stage complications

At present, sustained weight loss (of at least 7–10% of body weight) combined with regular physical activity is the only intervention consistently proven to reduce hepatic fat content, resolve NASH inflammation, and potentially reverse early fibrosis. No drug is currently approved specifically for NAFLD/NASH in most countries, although several agents are in late-stage clinical trials.

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Frequently Asked Questions

When is a person considered obese?

One of the simplest ways to assess your weight status is to calculate your Body Mass Index (BMI), a value obtained by dividing your weight in kilograms by your height in meters squared. A BMI above 25 is classified as overweight, and a BMI above 30 is classified as obese. While BMI has limitations (it does not distinguish muscle from fat), it remains a useful first-line screening tool. Your doctor can provide a more complete assessment using waist circumference and other parameters.

Do any supplements actually help with weight loss?

In short: no supplement produces clinically meaningful weight loss on its own. While some compounds (such as soluble fiber or green tea extract) may offer very modest ancillary effects on appetite or fat metabolism, no dietary supplement has been shown to be an effective weight loss treatment in the absence of dietary changes and physical activity. Many products marketed for weight loss are unregulated, unproven, and potentially harmful. Always consult a physician before using any supplement for this purpose.

Will skin remain loose after significant weight loss?

Skin elasticity after weight loss depends on several factors, such as age, genetics, and the amount of weight lost. Most importantly, however, it depends on the speed of weight loss. Rapid weight loss significantly increases the risk of excess, sagging skin, because the skin does not have sufficient time to gradually adapt and remodel. Losing weight gradually, at a rate of 0.5 to 1 kg per week, and combining dietary changes with regular strength training (to preserve and build muscle mass) substantially improves skin tone and elasticity. This approach also reduces the likelihood of post-weight-loss skin laxity.

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Sources and Bibliography

• NIH – Health Risks of Overweight & Obesity (NIDDK)
• SIEDP – National Consensus on Childhood Obesity Diagnosis, Treatment and Prevention
• Italian Guidelines for the Treatment of Obesity (SIO-ADI)
• The Lancet – Worldwide trends in body-mass index, underweight, overweight, and obesity (NCD Risk Factor Collaboration, Imperial College London & WHO, 2017)
• WHO – Controlling the Global Obesity Epidemic
• NCD Risk Factor Collaboration – Data Visualisations: Adiposity
• NCB – First 1000 Days and Metabolic Programming
• Jensen MD, et al. “2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults”. Circulation, 2014.
• IARC Working Group. “Body Fatness and Cancer: Viewpoint of the IARC Working Group”. New England Journal of Medicine, 2016.
• Wilding JPH, et al. “Once-Weekly Semaglutide in Adults with Overweight or Obesity”. New England Journal of Medicine, 2021.