While someone is losing weight through severe calorie restriction, the metabolism may slow down to protect the body's heat-producing store of calories, leading to a cold feeling.
First, when you're underweight, you lack an adequate level of body fat to insulate you from cold temperatures, Maggie Moon, RD, a Los Angeles–based nutritionist, told Health. Because having a low body weight may also mean you have low muscle mass, that could also be contributing to your chilliness.
Considerations. Cold intolerance can be a symptom of a problem with metabolism. Some people (often very thin women) do not tolerate cold temperatures because they have very little body fat to help keep them warm.
Human body temperature is inversely correlated with body mass.
Body Weight
Leaner people tend to sweat more efficiently and handle heat better than overweight individuals. Because fat acts as an insulator, people with excess fat may feel hotter, sweat more profusely and take longer to cool down than a leaner person .
New research from Macquarie University, published in the journal PLOS ONE, has found that both genders consider an unhealthily low body fat content for women as most attractive. Whereas the study found that both genders find men with a healthy level of body fat most attractive.
Low BMI. “Body fat insulates you from the cold, so if you don't have an adequate supply of it, you'll feel colder than others,” Dr. Moran explains. Patients with cancer or severe chronic diseases often lose body fat and tend to feel cold.
Thin people's subcutaneous layer lacks adipose tissue, but fat people's subcutaneous layer contains adipose tissue, which functions as an insulator and keeps the body warm. As a result, thin people feel colder than fat people.
According to Popular Science, studies done on both cold-water swimmers and hospital patients have shown that people with a higher Body Mass Index (BMI) are less susceptible to hypothermia because fat insulates the body's core.
"We always thought that fat (acting as insulation) was the most crucial factor in thermoregulation, but it's actually muscle playing the vital role. The body is this amazing, dynamic system which uses muscle to generate heat to keep the rest of the body warm, including your hands."
Lean people tolerate heat better than obese people. The more obese a person is, the less skin surface area the person has in relation to his or her weight. Greater surface area provides more exposed skin to perspire and cool the body through evaporation.
The numerous potential causes for coldness include hypothyroidism, calorie reduction and general aging, where people become more sensitive to cold temps due to a decrease in the metabolic rate and thinning of fat under the skin.
This is closely tied to the size of subcutaneous adipose tissue, or the fat beneath the surface of our skin. Fat is a great insulation material. The more subcutaneous fat a person has, the better their insulation is. The difference between how men and women respond to the cold is partly due to body shape.
Why am I always cold and tired? If any of these symptoms sound familiar, you may be dealing with a very common blood disorder called anemia. It affects more than 3 million Americans and over 1.6 billion people worldwide – and it's much more common in women and young children than in men.
Weakened immune system: your immune system is not 100% when you're underweight, so you're more likely to catch a cold, flu or other infections.
Losing weight has a profound effect on how you look. It can make you look more attractive and make you look a little older. The accompanying water consumption that goes with losing weight can clear up your skin and give you a nice glow.
Even when bodies are the same size, the amount of body fat inside can vary — and affect how cold or hot we feel in comparison to others. The greater the amount of body fat, the warmer one feels. Older people often might feel colder than younger people, as the fat layer under the skin that conserves heat thins with age.
But a University of Utah study published in the journal Lancet found that women's core body temperatures can actually run 0.4 degrees F higher than men's on average. And women's hands can be significantly colder — 82.7 degrees F on average, compared with 90 degrees F for men.
Scientists have found a reason why some people never seem to get warm while others never seem to feel the cold: some nerve cell receptors deep in the body are stimulated by signals other than temperature.
Those with heat intolerance may have a disorder called dysautonomia that affects their autonomic nervous system. The autonomic nervous system helps regulate automatic functions of the body, including the body's response to heat. Several medical conditions can cause dysautonomia, including: diabetes.
In fact, getting too lean can be actively unhealthy. You might end up with amenorrhea, low libido, disordered eating, bones like Swiss cheese, social isolation, and a host of other problems. Some elite bodybuilders rely on drugs like stimulants, diuretics, and other drugs just to keep themselves going.
According to the American Journal of Clinical Nutrition, there are healthy body fat percentages based on your age. For people aged 20 to 39, women should aim for 21% to 32% of body fat. Men should have 8% to 19%. For people 40 to 59, women should fall between 23% to 33% and men should fall around 11% to 21%.
Munzer's autopsy revealed he had almost 0 percent body fat, the legend goes. Such a small amount of body fat could have hastened his demise, experts say.