Hunger manifests across a spectrum, ranging from food insecurity to severe starvation. The journey from a simple lack of food to life-threatening starvation involves a series of physiological changes in the body. As food becomes scarce, the body begins to consume its own reserves, starting with a drop in energy levels, progressing to fat breakdown, and eventually muscle degradation. The final stages lead to critical organ failure. Currently, thousands of children under five and pregnant or lactating women in Gaza are suffering from acute malnutrition, while conflict in Sudan has pushed millions towards starvation, leading to urgent famine warnings.
Nutritionists Ola Anabtawi and Berta Valente explain the complex science behind starvation and its impact on the human body when deprived of food.
Minimum Nutritional Needs for Survival
Survival requires more than just clean water and safety; access to adequate food is vital. It is essential to meet daily energy, macronutrient, and micronutrient requirements to maintain health and prevent malnutrition. According to the World Health Organization (WHO), energy needs vary based on age, sex, and activity level.
Energy is measured in kilocalories (kcal), indicating how much energy a person derives from food or needs to function. One kilocalorie is defined as the energy required to raise one kilogram of water by one degree Celsius. The body utilizes energy for essential functions such as breathing, digestion, and, crucially for children, growth.
Total energy requirements stem from three primary sources: resting energy expenditure, physical activity, and thermogenesis. Resting energy expenditure is the energy used by the body at rest for vital functions, while physical activity can vary, particularly in emergencies. Thermogenesis accounts for the energy used in digesting and processing food.
Energy needs evolve through different life stages. For instance, infants require approximately 95 kcal to 108 kcal per kilogram daily in the first six months, decreasing to 84 kcal to 98 kcal per kilogram from six to twelve months. A two-year-old typically needs around 1,000 kcal to 1,200 kcal daily, while a five-year-old requires about 1,300 to 1,500 kcal. By the age of ten, energy requirements start differing between boys and girls due to growth and activity variations.
For adults aged 19 to 50, men generally need about 2,900 kcal daily, while women require approximately 2,200 kcal. These figures allow for a 20% variance to accommodate individual differences. As people age, energy needs slightly decrease, with men over 50 requiring about 2,300 kcal and women needing around 1,900 kcal.
In humanitarian emergencies, food aid must ensure a minimum intake of 2,100 kcal per person per day to maintain basic health and function. This energy should come from a balanced mix of macronutrients: 50%-60% carbohydrates, 10%-35% proteins, and 20%-35% fats. Young children and pregnant or breastfeeding women require higher fat percentages to support growth and development.
Physiological Effects of Starvation
Starvation triggers a series of overlapping physiological responses as the body strives to survive without food. The first stage, lasting up to 48 hours post-food intake, involves utilizing glycogen stored in the liver to stabilize blood sugar levels, a process known as glycogenolysis. When glycogen is depleted, the body enters the second stage, gluconeogenesis, where it produces glucose from non-carbohydrate sources such as amino acids from muscle. This metabolic shift fuels essential organs but leads to muscle breakdown and increased nitrogen loss.
By the third day, the body primarily relies on ketogenesis, converting fatty acids into ketones, which serve as an alternative energy source. This adaptation helps spare muscle tissue but signifies a deeper metabolic crisis. Hormonal changes, including decreased insulin and thyroid hormone activity, slow the metabolic rate to conserve energy. Eventually, once fat stores are exhausted, the body must break down its own proteins for energy, leading to accelerated muscle wasting and heightened vulnerability to infections.
The visible effects of starvation are stark: significant weight loss, muscle wasting, fatigue, and compromised immune function. Individuals may experience dry skin, hair loss, and slowed heart rates. Starvation also inflicts psychological distress, manifesting as apathy, irritability, anxiety, and a constant preoccupation with food. Cognitive abilities decline, and emotional regulation deteriorates, which can lead to depression or social withdrawal. In children, the long-term consequences include stunted growth and impaired brain development, with potential for irreversible damage.
The impact of starvation extends beyond the individual, fracturing families and communities. As energy levels plummet, people struggle to care for themselves and others. In humanitarian crises like those in Gaza and Sudan, starvation compounds the trauma of violence and displacement, leading to a complete collapse of social and biological resilience.
Breaking the Cycle of Starvation
After a period of starvation, the body enters a fragile metabolic state. Rapid reintroduction of food, particularly carbohydrates, can lead to refeeding syndrome, causing serious complications such as heart failure or respiratory distress. This condition arises from a spike in insulin and a rapid shift of electrolytes like phosphate, potassium, and magnesium into cells.
Standard protocols for recovery begin with therapeutic milks like F-75, designed to stabilize patients during the initial treatment phase for severe acute malnutrition. This is followed by ready-to-use therapeutic food—often a peanut-butter paste or biscuit—that can help malnourished children recover fully in four to eight weeks. Oral rehydration salts and micronutrient powders are also critical components of recovery.
Safe delivery of these resources is paramount. Consistent humanitarian access is essential, as airdrops alone do not constitute food security. Sustainable efforts to restore food systems, protect civilians, and uphold humanitarian law are necessary to prevent repeating cycles of hunger and suffering. When food assistance is inadequate in quality or quantity, or when clean water is unavailable, the risk of worsening malnutrition escalates.
The authors declare no affiliations or funding sources that would benefit from this article beyond their academic appointments.
