The hidden biology of weight struggles – it’s not laziness 

May 13, 2025 | Weight loss

Introduction 

Those who struggle to lose weight are often met with unfair judgments. One of the most harmful misconceptions is that people who don’t lose weight must simply be lazy, undisciplined, or unmotivated. But the truth is far more complex. 

Weight gain—and difficulty losing weight—is not a reflection of willpower. It’s the result of intricate biological, psychological, and environmental factors that can make sustained weight loss an uphill battle. Let’s take a closer look at the science. 

 

Obesity is a chronic, relapsing disease 

Obesity is not a lifestyle choice; it’s a chronic medical condition with a complex web of contributing factors. According to the World Health Organisation and Australian Department of Health, obesity is driven by dysregulated energy balance, hormonal imbalances, genetic predisposition, and environmental triggers (Australian Department of Health and Aged Care, 2023). 

Like diabetes or hypertension, obesity is long-term and relapsing, meaning symptoms can return even after periods of improvement. This is why losing weight—and keeping it off—is not as simple as “eating less and moving more.” 

 

The role of genetics 

Research shows that genetics account for 40–70% of a person’s susceptibility to obesity (Loos & Yeo, 2022). Genes influence: 

  • Appetite regulation 
  • Basal metabolic rate (BMR) 
  • Fat storage and distribution 
  • Response to hunger hormones 

For example, some people are genetically wired to feel less full after meals or to have a lower resting metabolism, meaning they burn fewer calories at rest. Others have heightened sensitivity to food cues—making them more likely to overeat in response to stress or anxiety. 

Hormonal and metabolic factors 

Weight loss often triggers biological responses that fight to restore lost weight—a survival mechanism rooted in our evolution. 

Key hormones affected during and after weight loss include: 

  • Leptin: Decreases with weight loss, making you feel hungrier 
  • Ghrelin: Increases with weight loss, also increasing hunger 
  • Insulin: Becomes more efficient at storing fat when calorie intake drops 

In addition, the body often reduces resting metabolic rate during weight loss. This phenomenon, called adaptive thermogenesis, means your body burns fewer calories, making it even harder to maintain weight loss (Rosenbaum & Leibel, 2010). 

So, when someone says they’re eating less but not losing weight, it’s entirely plausible—their body is fighting back. 

 

Medications and medical conditions 

Certain medical conditions and medications can impair metabolism or increase weight gain, regardless of behaviour. These include: 

  • Hypothyroidism 
  • Polycystic Ovary Syndrome (PCOS) 
  • Insulin resistance and type 2 diabetes 
  • Cushing’s syndrome 
  • Antidepressants, antipsychotics, and corticosteroids (Wharton et al., 2020) 

People dealing with these conditions may find it harder to lose weight or maintain energy for exercise and blaming them for a biological reality can sometimes even be harmful. 

 

Psychological and environmental influences 

Stress, trauma, and mental health conditions such as depression or anxiety can increase emotional eating, reduce motivation, or disrupt sleep—all of which impact weight. Trauma survivors, particularly those with childhood adversity, may have altered cortisol levels and coping mechanisms that lead to long-term weight issues (Felitti et al., 1998). 

Environmental and social determinants also play a role: 

  • Food insecurity and low socioeconomic status 
  • Limited access to healthy food 
  • Lack of safe spaces for exercise 
  • Cultural and family eating patterns 

None of these are indicators of laziness—they are reflections of lived experiences, inequity, and biology. 

 

Why weight loss is harder for some people 

Here’s a summary of why two people can follow the same diet but experience vastly different results: 

Factor 

Impact on Weight Loss 

Genetics 

Affects metabolism, hunger, and fat storage 

Hormones 

Can trigger hunger and slow metabolism after weight loss 

Medical conditions 

Impair energy use or promote fat gain 

Medications 

May cause weight gain as a side effect 

Psychological stress 

Triggers emotional eating or low motivation 

Environment 

Influences food choices and activity levels 

Understanding this variability helps us move away from blame and toward support. 

 

Final thoughts 

Weight gain and difficulty losing weight are not signs of laziness. They are symptoms of a complex, multifactorial condition—not a personal failing. 

Blaming individuals for their weight can lead to shame, disordered eating, and avoidance of medical care. Instead, we should offer empathy, evidence-based tools, and support. 

If you’re struggling to lose weight, know this: you are not lazy. You are dealing with a challenge that deserves the same compassion and medical attention as any other chronic health issue. 

 

References 

Australian Department of Health and Aged Care. (2023). Obesity and overweight. https://www.health.gov.au/health-topics/obesity-and-overweight 

Felitti, V. J., Anda, R. F., Nordenberg, D., Williamson, D. F., Spitz, A. M., Edwards, V., … & Marks, J. S. (1998). Relationship of childhood abuse and household dysfunction to many of the leading causes of death in adults. American Journal of Preventive Medicine, 14(4), 245–258. https://doi.org/10.1016/S0749-3797(98)00017-8 

Loos, R. J. F., & Yeo, G. S. H. (2022). The genetics of obesity: From discovery to biology. Nature Reviews Genetics, 23(2), 120–133. https://doi.org/10.1038/s41576-021-00414-z 

Rosenbaum, M., & Leibel, R. L. (2010). Adaptive thermogenesis in humans. International Journal of Obesity, 34(S1), S47–S55. https://doi.org/10.1038/ijo.2010.184 

Wharton, S., Lau, D. C. W., Anderson, C., Bondy, G. P., Chaudhury, T. K., Goldstein, D., … & Sharma, A. M. (2020). Obesity in adults: A clinical practice guideline. Canadian Medical Association Journal, 192(31), E875–E891. https://doi.org/10.1503/cmaj.191707 

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Medically reviewed by Dr Matt Cullen
MBBS, FRANZCP

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