Weight loss is often simplified as “eat less, move more,” but for many, the journey is far from straightforward. If you’ve faced slow progress, frustrating plateaus, or regained weight, know that you’re not alone and it’s not your fault.
Dr. Jennah Siwak, a board-certified Family and Obesity Medicine physician (and known as @drjennahsiwak on social media), explains that these challenges are rooted in a mix of biology, genetics, environment, and even how our brains are wired.
In this guide, Dr. Siwak offers evidence-based insights and compassionate advice to help you understand why losing weight is difficult, while providing practical strategies to approach your journey with greater self-compassion, resilience, and lasting success.
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Your Brain Is Wired to Fight Weight Loss
“Much of our eating behavior happens beneath our conscious awareness,” explains Dr. Siwak. “Nobody wakes up thinking, ‘I want to overeat and harm my health.’” Yet our brains—particularly the hypothalamus—have evolved to regulate and defend body weight, often resisting weight loss more strongly than weight gain. This reflects an evolutionary bias toward survival and preventing starvation.
This “lipo-stat” system reacts to fat loss by triggering hunger and cravings, often without us realizing it. When leptin, a hormone produced by fat cells, drops during weight loss, the brain interprets it as starvation, increasing hunger and slowing metabolism.
“This system was built for survival in an environment of scarcity,” says Dr. Siwak. “Now it’s navigating a world of ultra-processed, calorie-dense foods, and our ancient brain circuits are overwhelmed.”
Genetics Plays a Bigger Role Than You Might Think
“Some people seem to eat whatever they want and not gain weight, while others have to be incredibly careful,” notes Dr. Siwak. This isn’t just anecdotal—genetic research supports it.
Studies suggest that 40–70% of body mass index (BMI) is influenced by genetics. But as Dr. Siwak points out, genes don’t act alone. “Genetics load the gun, but environment pulls the trigger.”
In other words, weight is not simply a matter of willpower. Biology plays a major role, interacting with lifestyle and environmental factors to shape each person’s unique weight journey.
Metabolism Slows Down During Weight Loss
One of the most frustrating aspects of losing weight is that it often gets harder over time. That’s because your metabolism adjusts in response to weight loss.
“When you lose weight, your body sees it as a threat,” explains Dr. Siwak. “Hunger increases, metabolism slows, and you burn fewer calories, even at rest.”
This metabolic adaptation is your body’s way of protecting itself. For people with obesity, the body may defend a higher baseline weight, making long-term weight maintenance especially challenging.
Dr. Siwak compares it to a thermostat: “Imagine your body is set to 80°F. You can open a window to cool it down, but the heating system kicks in to bring it back to 80. That’s what your brain is doing with fat stores.”
Stress, Sleep, and Emotions Affect Eating Behavior
Stress and poor sleep don’t just impact your mood—they directly influence hunger hormones, decision-making, and self-control.
“Impulsivity increases when we’re sleep-deprived or stressed,” explains Dr. Siwak, meaning the brain’s logical control center struggles to override cravings and urges.
Chronic stress can lead to emotional eating, while inadequate sleep disrupts key appetite-regulating hormones like ghrelin and leptin.
For this reason, Dr. Siwak emphasizes that prioritizing sleep and managing stress are essential strategies for supporting your weight goals, helping your brain and body work together rather than against you.
Considering Environmental and Medical Challenges
Where you live, work, and what food is accessible can significantly influence your ability to lose weight. Dr. Siwak notes that people with long or irregular work hours—like night shifts—often experience disrupted circadian rhythms, which can affect hunger and metabolism.
In areas known as food deserts, healthy options may be limited, pushing people toward processed, high-calorie foods. “If you don’t have a healthy lunch packed, you’re likely to grab what’s fast and convenient,” she says.
Certain medications can also contribute to weight gain, including:
- Antidepressants (e.g., paroxetine, amitriptyline)
- Mood stabilizers (e.g., lithium, quetiapine)
- Diabetes medications (e.g., insulin)
- Steroids, antihistamines, and some birth control methods
“Sometimes these medications are necessary, and their benefits outweigh the risks, but talk with your doctor before stopping any medication,” Dr. Siwak advises.
Evaluating Weight Loss Plateaus
First, Dr. Siwak recommends confirming whether you’re truly experiencing a plateau. “Weight loss isn’t linear,” she says. “Check your menstrual cycle, hydration, and digestion. Weight fluctuations are normal.”
If you’re no longer in a calorie deficit which becomes harder as metabolism slows—weight loss will stall. This isn’t a reflection of failure; it’s your body maintaining stability.
She suggests re-evaluating:
- Food intake
- Stress
- Sleep
- Physical activity
- Medications
Metabolic adaptations and hormonal changes can also reduce unconscious movement, known as non-exercise activity thermogenesis (NEAT), further slowing progress.
Keeping the Weight Off
Maintaining weight loss requires long-term strategy and consistency:
- Prioritize protein, fiber, and healthy fats to stay full.
- Avoid rapid, extreme diets they’re harder to sustain.
- Stay active with both cardio and strength training.
- Check in regularly with habits and progress (weight, food logs, movement).
- Build in recovery days and vary exercise intensity.
- Focus on sleep, stress management, and community support.
The goal isn’t perfection; it’s consistency.
Setting Realistic Goals and Timelines
The recommended rate of weight loss is 1–2 pounds per week for six months. Faster weight loss can lead to muscle loss, metabolic slowdown, and regain.
Achieving a Calorie Deficit
“You must be in a calorie deficit to lose weight,” Dr. Siwak says. “How you create that deficit—whether through intermittent fasting, low-carb, or portion control—depends on what works for you.”
The best diet is one that fits your lifestyle, preferences, and schedule—one you can sustain long-term.
Understanding Your Body
“Weight loss is extremely difficult,” Dr. Siwak emphasizes. “Your body is designed to defend its fat stores. Struggling isn’t a sign of weakness it’s a sign your biology is doing exactly what it was built to do.”
Her top message for anyone feeling discouraged:
“You are stronger than you think. Understanding your body helps you work with it, not against it.”
This means recognizing how hunger hormones, metabolism, stress, sleep, and medications influence weight—not as excuses, but as factors to manage thoughtfully and strategically.
Frequently Asked Questions
Why is losing weight so difficult for some people?
Weight loss isn’t just about willpower. Biology, genetics, metabolism, hormones, stress, sleep, medications, and the environment all influence your ability to lose and maintain weight. Your brain and body are designed to defend fat stores, making the process challenging.
What is a weight loss plateau, and why does it happen?
A plateau occurs when weight loss stalls despite continued effort. This can result from slowed metabolism, hormonal changes, reduced activity, or returning to maintenance-level calorie intake. Fluctuations are normal, and plateaus are part of the process.
How does metabolism affect weight loss?
When you lose weight, metabolism slows, and your body burns fewer calories at rest. This metabolic adaptation is your body’s way of maintaining stability, which can make continued weight loss more difficult.
Can genetics impact my ability to losZe weight?
Yes. Research suggests 40–70% of BMI is influenced by genetics. However, environment and lifestyle also play critical roles. Genetics may predispose you to gain weight, but choices and habits still matter.
How do stress and sleep affect eating habits?
Chronic stress and poor sleep disrupt hunger hormones and increase impulsivity, cravings, and emotional eating. Prioritizing stress management and adequate sleep supports weight goals.
Do medications affect weight loss?
Certain medications like antidepressants, mood stabilizers, diabetes medications, steroids, antihistamines, and some birth control can contribute to weight gain. Always consult your doctor before making changes to prescribed medications.
Conclusion
Weight loss is rarely a straight path, and it’s not simply a matter of willpower. Biology, genetics, metabolism, hormones, sleep, stress, environment, and even medications all influence how your body responds to efforts to shed pounds. Understanding these factors is key to approaching weight loss with compassion, patience, and strategy. Dr. Siwak emphasizes that struggling doesn’t mean failure it’s a reflection of how your body is designed to protect itself.
