Understanding Anorexia Nervosa: Metabolic Adaptations and Nutritional Considerations

Understanding Anorexia Nervosa Through a Naturopathic Lens: Metabolic Adaptations and Nutritional Considerations

Anorexia nervosa is a complex biopsychosocial condition predominantly affecting teenage girls, characterised by extreme restriction of food intake and significant weight loss. Beyond its psychological roots, the condition profoundly alters metabolic and endocrine functions, mirroring the body’s response to prolonged starvation. As a naturopath, understanding these metabolic pathways provides valuable insights into supporting recovery and optimising care.

Signs and Symptoms of Anorexia Nervosa

Individuals with anorexia nervosa exhibit severe weight loss, often dropping below 85% of their ideal body weight or maintaining a body mass index (BMI) under 17.5 kg/m². Common signs include:

• Fear of gaining weight despite being underweight.
• Disrupted growth and development in adolescents.
• Loss of adipose and lean body mass, decreased bone density.
• Impaired organ function, including cardiovascular and gastrointestinal systems.
• Hormonal imbalances and nutrient deficiencies.
• Physical manifestations such as dry, brittle hair and skin (Gropper, Smith, & Groff, 2004, p. 547).

The severe protein-calorie deprivation seen in anorexia nervosa triggers the body’s metabolic adaptations to conserve energy and prioritise survival.

Metabolic Pathways in Anorexia Nervosa

The pathophysiology of anorexia nervosa aligns closely with starvation physiology. The body initiates mechanisms to reduce protein degradation, shift to alternative fuel sources, and minimize energy expenditure.

Carbohydrate Metabolism

Glucose, the body’s primary energy source, is crucial for maintaining homeostasis. In starvation:

• Glycogen stores in the liver and muscle are rapidly depleted within hours.
• The liver uses glucokinase to convert glucose to glucose-6-phosphate, retaining glucose for cellular energy (Berg et al., 2007, p. 615).
• The brain’s glucose requirement decreases from 120 g/day to 40 g/day as ketone bodies replace glucose as a primary fuel source (Berg et al., 2007, p. 807-813).
• Hyperglycemia and insulin resistance may occur, driven by hormonal changes that stimulate gluconeogenesis and glycogenolysis to provide glucose for glucose-dependent tissues like red blood cells (Sharma, Mogensen, & Robinson, 2019, p. 14).

Fat Metabolism

As carbohydrate stores deplete, the body shifts to fats as its primary energy source:

• Fatty acids, stored as triacylglycerols in adipose tissue, are mobilized for energy.
• In the liver, fatty acids are converted to ketone bodies—acetoacetate and β-hydroxybutyrate—which are water-soluble and used by most tissues, including the brain, muscle, and kidney (Pelley, Goljan, & Pelley, 2017, p. 109-117).
• Ketosis emerges as a hallmark of starvation, conserving glucose for red blood cells, which rely solely on glucose for energy (Sharma et al., 2019, p. 15).

However, fatty acid metabolism has limitations:

• Fat conversion to ATP requires substantial oxygen and mitochondrial integrity, both compromised during prolonged starvation.
• Stress hormones like epinephrine stimulate lipase, releasing free fatty acids (FFA) and glycerol, which may accumulate and disrupt cellular respiration, leading to metabolic acidosis (Pelley et al., 2017, p. 109-117).

Protein Metabolism

Protein serves as a vital glucose precursor during starvation:

• Amino acids from dietary proteins or muscle catabolism provide substrates for gluconeogenesis (Berg et al., 2007, p. 674).
• Muscle protein breakdown slows initially, but as starvation progresses, proteins become the predominant energy source. This accelerates nitrogen loss and muscle wasting.
• The loss of functional protein reserves contributes to organ dysfunction and poor immune response (Sharma et al., 2019, p. 14).

Naturopathic Considerations for Supporting Recovery

The recovery process in anorexia nervosa requires careful metabolic and nutritional restoration to avoid refeeding syndrome and ensure sustainable healing.

Reintroducing Nutrition

1. Carbohydrates: Gradual reintroduction of complex carbohydrates helps restore glycogen stores and stabilise blood sugar levels. Foods like oats, quinoa, and sweet potatoes provide steady energy without overloading insulin pathways.
2. Fats: Emphasising healthy fats, such as omega-3s from flaxseed, chia seeds, and fish oil, supports brain function and anti-inflammatory pathways.
3. Proteins: High-quality protein sources, such as eggs, lentils, and lean poultry, are essential for repairing muscle and restoring organ function. Monitoring nitrogen balance can guide protein intake.

Supporting Metabolic Adaptation

• Ketone Utilisation: Incorporating MCT oil may help bridge the transition from ketone reliance to glucose-based metabolism.
• Micronutrient Replenishment: Zinc, magnesium, and B vitamins are often depleted and play crucial roles in enzymatic functions and energy production.
• Probiotics: Gut health is frequently compromised; probiotics and prebiotic-rich foods like bananas and asparagus aid in restoring the microbiome.

Holistic Support

1. Stress Management: Techniques such as mindfulness, yoga, and acupuncture can reduce cortisol levels, improving metabolic resilience.
2. Monitoring Hormonal Health: Addressing thyroid and adrenal imbalances with adaptogenic herbs like Withania and Rhodiola can enhance recovery.
3. Bone Health: Supplementing with calcium, vitamin D, and weight-bearing exercises supports bone density recovery.

Conclusion

Anorexia nervosa is a multifaceted condition with profound metabolic consequences. By understanding the body’s adaptive responses to starvation—shifting from glucose to fat and protein metabolism—naturopaths can craft personalised strategies to support recovery. Nutritional therapy, combined with holistic care, provides a comprehensive approach to restoring health and resilience in individuals overcoming this condition.

References

• Berg, J. M., Tymoczko, J. L., & Stryer, L. (2007). Biochemistry. W. H. Freeman.
• Gropper, S. S., Smith, J. L., & Groff, J. L. (2004). Advanced Nutrition and Human Metabolism. Wadsworth.

• Mahan, L., & Raymond, J. (Eds.). (2017). Krause’s food & the nutrition care process (Fourteenth ed.). St. Louis, Missouri: Elsevier.

• Pelley, J. W., Goljan, E. F., & Pelley, R. J. (2017). Rapid Review Biochemistry. Elsevier Health Sciences.

• Scherholz, M., Schlesinger, N., & Androulakis, I. (2019) Chronopharmacology of glucocorticoids. Advanced Drug Delivery Reviews, 151-152, 245-261. doi:10.1016/ j.addr.2019.02.004

• Sharma, S., Mogensen, K. M., & Robinson, M. K. (2019). Nutritional management in critical illness: Starvation, refeeding, and metabolic response.

• Ttatty, (2020, April 1).[Background Photo]. Retrieved from https:// www.istockphoto.com/au/photo/anorexic-body- gm485411993-37250902