What causes weight gain?

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From the Guidelines

Weight gain is primarily caused by consuming more calories than the body burns, leading to a caloric surplus and storage of excess energy as fat, with key contributing factors including poor dietary choices, sedentary lifestyle, inadequate sleep, stress, and certain medications, as supported by the most recent and highest quality study 1. When considering the causes of weight gain, it's essential to look at the balance between energy intake and expenditure. Several factors contribute to weight gain, including:

  • Poor dietary choices, especially foods high in sugar, refined carbohydrates, and unhealthy fats
  • Sedentary lifestyle
  • Inadequate sleep
  • Stress
  • Certain medications, such as antidepressants, mood stabilizers, corticosteroids, and some diabetes medications
  • Hormonal changes, particularly during menopause or with thyroid disorders
  • Genetics
  • Aging, which naturally slows metabolism Medical conditions like hypothyroidism, polycystic ovary syndrome (PCOS), and Cushing's syndrome can also cause weight gain. To prevent unwanted weight gain, it's crucial to focus on:
  • Balanced nutrition with appropriate portion sizes
  • Regular physical activity, aiming for at least 150 minutes of moderate exercise weekly
  • Adequate sleep, 7-9 hours nightly
  • Stress management
  • Limiting alcohol consumption The body maintains weight through a complex system balancing energy intake and expenditure, regulated by hormones like insulin, leptin, and ghrelin that influence hunger, satiety, and metabolism, as noted in 1 and 1. Additionally, certain medications can promote weight gain, and healthcare professionals should carefully review concomitant medications and consider alternatives that minimize or avoid weight gain, as recommended in 1. A comprehensive approach to weight management, including lifestyle modifications and, when necessary, pharmacotherapy or other interventions, is essential for preventing and treating weight-related issues, as outlined in 1.

From the FDA Drug Label

orlistat works by preventing the absorption of some of the fat you eat. for every 5 pounds you lose from diet alone, orlistat can help you lose 2-3 pounds more. The question is about what causes weight gain.

  • The provided drug label does not directly address the causes of weight gain, but rather how orlistat works to help with weight loss.
  • Weight gain is not explicitly mentioned as a cause in the label. The FDA drug label does not answer the question.

From the Research

Causes of Weight Gain

  • Weight gain is associated with many serious health conditions, including type II diabetes mellitus, hypertension, and coronary heart disease 2
  • Gaining weight, even if a person remains within the "normal" weight range, increases the risk of medical illnesses and premature death 2
  • A small positive energy balance over time can cause weight gain in many individuals 3
  • Low levels of physical activity and poor dietary habits contribute to an increased risk of obesity 3
  • Medications can also cause weight gain, with iatrogenic obesity being a contributing factor to a patient's obesity 4
  • Emotional/mental health issues, physical health, and influence of significant others can also lead to weight gain 5
  • Lack of self-regulation skills, negative mood and stress, and lack of self-efficacy for healthy eating or physical activity are barriers to weight loss 5
  • Hormonal changes, such as those experienced during menopause, can also lead to weight gain and changes in body fat distribution 6

Factors Contributing to Weight Gain

  • Poor eating habits 2, 3, 5
  • Lack of physical activity 2, 3, 5
  • Emotional/mental health issues 5
  • Physical health problems 5
  • Influence of significant others 5
  • Medications 4
  • Hormonal changes 6
  • Lack of self-regulation skills 5
  • Negative mood and stress 5
  • Lack of self-efficacy for healthy eating or physical activity 5

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Physical and psychological consequences of weight gain.

The Journal of clinical psychiatry, 1999

Research

Iatrogenic Obesity.

Endocrinology and metabolism clinics of North America, 2020

Research

Factors Related to Weight Gain/Loss among Emerging Adults with Obesity.

American journal of health behavior, 2018

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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