When you think about heatwave health risks, obesity and poor fitness are often blamed first. However, doctors warn that extremely slim or underweight individuals may also face serious dangers during high temperatures. As it continues to be a super hit with temperatures across the country touching 48 degrees Celsius in some places, health experts say low body fat, poor nutrition, dehydration, and reduced muscle mass can make some thin individuals surprisingly vulnerable to heat exhaustion and heatstroke. Also read: Heatstroke Doesn’t Always Feel Hot: Strange Symptoms Most People Miss Why body fat matters during heatwaves? Body fat is not always harmful. In fact, experts say a healthy amount of fat helps the body regulate temperature, store energy, and maintain hydration balance during stressful conditions. Very slim men, women, and children often have: Lower energy reserves Reduced electrolyte storage Less muscle mass Lower blood volume Poor heat tolerance During intense heat, the body works harder to cool itself through sweating and increased blood circulation. If the body lacks sufficient fluid reserves or nutrients, dehydration and exhaustion can happen faster. Muscle loss and heat sensitivity Muscles play an important role in maintaining circulation, metabolism, and overall physical stability. Those who have low muscle mass - including some underweight individuals, crash dieters, elderly adults, or those with eating disorders- may struggle more during prolonged heat exposure. Experts warn that heatwaves can increase weakness, dizziness, low blood pressure, fatigue, and fainting episodes. In severe cases, this may progress to heatstroke, a potentially life-threatening condition where body temperature rises dangerously high. Why does dehydration hit slim people faster? Doctors say slim individuals sometimes underestimate how quickly dehydration affects them. Because smaller bodies often hold lower fluid reserves, excessive sweating during hot weather can rapidly disturb electrolyte balance, especially sodium and potassium levels. Symptoms of dehydration may include: Dry mouth Headache Muscle cramps Rapid heartbeat Confusion Dark urine Nausea Heatwaves and nutritional deficiencies Health experts also warn that restrictive dieting, poor eating habits, or inadequate protein intake can worsen heat intolerance. Many people trying to lose weight during summer may unintentionally reduce salt intake, water intake, essential minerals and calorie intake. This can impair the body’s ability to recover from heat stress. Doctors say undernourished individuals may feel: Extreme tiredness Brain fog Weakness Trouble concentrating Increased irritability during heatwaves Elderly slim adults face a higher risk Older adults who are naturally thin or frail are especially vulnerable because aging already reduces the body’s ability to regulate temperature efficiently. Many elderly individuals also experience reduced thirst sensation, chronic illnesses, lower muscle mass, and medication-related dehydration. Health experts say these factors can dramatically increase heatstroke risk during prolonged high temperatures. How to stay safe during heatwaves? Doctors recommend several precautions for slim or underweight individuals during extreme heat: Drink water regularly, even before feeling thirsty Maintain balanced meals with electrolytes and protein Avoid extreme dieting during heatwaves Stay indoors during peak afternoon temperatures Wear lightweight cotton clothing Monitor dizziness, weakness, or confusion carefully