Caution with obesity in the summer heat

In hot weather, the body needs to lose excess heat in order to keep its core temperature stable, and sweating is one obvious way to achieve this. Glands exude sweat to the surface of the skin, where it evaporates. The cooling effect caused by evaporation removes heat from the body. Besides sweating, the body increases the blood flow to the skin. An increased amount of warmer blood from inside the body is channelled to the cooler extremities, where it emits heat. 

Excess weight can have a significant adverse impact on these natural cooling mechanisms. A study published in the specialist journal Nature in 2018 indicated that there is a positive correlation between obesity and body temperature in men and postmenopausal women. Researchers found that not only do subcutaneous fat reserves act as a layer of insulation, hindering heat exchange and therefore the cooling process, but that overweight people produce more heat. On the one hand, the higher body mass increases the basal metabolic rate and, on the other, the metabolically active adipose tissue results in the secretion of numerous hormones and semiochemicals that affect heat regulation. 

Further studies revealed that physical activity undertaken by obese people at high temperatures result in a higher rise in body temperature and heart rate than people of an average weight – and are therefore placed under greater strain. 

If the outside temperature is roughly the same as the body temperature (36–37°C) or higher, the body’s cooling mechanisms can be pushed to their limits. The first signs of heat stress are dizziness and headache, followed by confusion, nausea and vomiting. If the body is not cooled and/or fails to receive sufficient fluids, the blood pressure may drop so dramatically that not enough blood is pumped to the organs. In turn, this may result in a loss of consciousness and damage to all organ systems. 

Just like elderly people and children, overweight individuals are more susceptible to heat stress and should therefore ensure that they drink enough fluids and seek out the shade in hot weather. Physical exertion should be avoided in hot temperatures, as this places a considerable strain on the cardiovascular system. 

Consequently, activity in moderation, a shady spot and a bottle of water to hand represent the best strategy when it comes to getting through the hottest days of the year safe and sound.