Homeostasis
In fields like medicine and cellular biology, a pivotal concept is homeostasis.
“Homeostasis is the state of steady internal, physical and chemical conditions in the internal environment.” – Walter Cannon
Coined in the early 20th century by physiologist Walter Cannon, the term “homeostasis” merges two Greek words: “homois” (similar) and “stasis” (steady). It aptly describes the body’s aptitude to regulate its internal environment to sustain a constant condition.
Disease in medicine often stems from either temporary or chronic disturbances in this physical and/or chemical balance, underscoring the significance of understanding human body’s various homeostatic states.
Weight Loss in the Context of Homeostasis
Before delving into weight loss, it’s pivotal to note that the body’s regulation of weight is chiefly designed to uphold energy balance through several means.
- Neural mechanisms
- Hormonal influences
- Metabolic rate
- Feedback loops
- Environmental and behavioural factors
- Genetic determinants
Neural
Central to energy balance regulation, the hypothalamus governs feeding behaviour and energy expenditure.
i) Neuropeptide Y and agouti-related peptide (AgRP) neurons in the hypothalamus stimulate food intake.
ii) Proopiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript neurons in the hypothalamus curtail food intake.
Hormonal
i) Leptin: Generated by fat cells (adipocytes), leptin conveys the energy storage level to the brain, with high levels typically dampening appetite.
ii) Insulin: Released by pancreatic cells, it relays nutrient status to the brain besides its central role in glucose regulation.
iii) Ghrelin: Originating in the stomach, ghrelin heightens appetite, often surging before meals. iv) Peptide YY and Cholecystokinin: Elicited by food intake, these gut hormones mainly act as satiety indicators.
Metabolic Rate
The basal metabolic rate (BMR) denotes energy expended at rest and is modulated by factors like age, muscle mass, and thyroid hormones.
Challenges in Weight Loss and Maintenance:
Given that your pre-weight loss body weight is considered “normal” by your physiological mechanisms (particularly if maintained over extended periods), any deviation is deemed irregular. Consequently, after shedding weight, the aforementioned homeostatic systems activate, curbing further weight loss and prompting weight regain. In simpler terms, your body drives you towards feeling extremely hungry, lethargic, and below par.
Overriding this challenging physiological response requires sheer determination, barring interventions like bariatric surgery or weight loss medications.
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