How come people from very cold climates can visit LA in the winter and walk around in shirts and shorts?

Doesn’t 55°F feel the same for everybody?!

Nope, it doesn’t! As long as their vacation is just for a week or two, they would totally feel like this LA weather, even at night, is pretty warm!

When your body temperature is dropping because it’s been consistently cold over several days or weeks, your body ramps up production of your thyroid hormone. Your thyroid hormone is what regulates your metabolism. And your metabolism is only about 40% efficient, meaning that when sugars/fats/proteins are converted to usable energy (ATP), about 40% of the original molecules are used as ATP, and 60% is given off as heat. This is why your body is 98.6°F (37°C), meaning all these metabolic processes are giving off lots of heat!  Your car engine, is about 20% efficient.  About 80% of the gasoline being burned is wasted in the form of heat, hence why that engine oil and exhaust is scalding hot!

So anyway, when the temperatures get colder… the thyroid hormone production increases, causing your metabolism to increase, CAUSING YOUR BODY TO GENERATE MORE HEAT.  This then causes you to feel HUNGRY because food is the fuel to supplement this energy production. This is why places like Minnesota are called “Meat and Potatoes Country.”  During the winter months, you may have an insatiable appetite due to this ramped up basal metabolism. It doesn’t help that we have all these holiday dinners (thanksgiving/christmas) placed at the perfect time. And of course since we wear long sleeves and big coats which helps to hide the fat, we gain weight without even realizing it.

Now, when the temperatures start warming up and your body isn’t struggling to always stay warm, thyroid production will decrease. When temperatures get downright hot and humid, thyroid production will decrease even further, to slow down metabolism. This is why in the heat, people don’t have a big appetite. Instead of having giant meals like they would’ve in the winter, they rather have light salads in the summer time.

So when a person is visiting LA from Minnesota, their base metabolic rate is very high compared to ours.  When they come here and it’s 55°F out, they can stay out here in shirts and shorts and feel fine. Eventually though, their bodies will acclimate of course. Hope that helps.  🙂

Related articles if that was interesting to you:

• Physiology: Regulation of Body Temperature
• Physiology: Thy­rotropin (what stimulates your thyroid)
• Anatomy: The Endocrine Sys­tem (Pitu­itary, Thy­roid, Pan­creas, Adrenal, Gonads, etc)
• Pharmacology: Con­se­quences of a Low Iodide Diet
• Pharmacology: Hypothy­roidism
• Pharmacology: Hyper­thy­roidism