Many other small, temporary stresses can provoke the sort of hormetic response that we've covered throughout this book.

One common stress that organisms have had to endure is cold. Wim Hof is known as the Iceman for his exploits involving prolonged exposure to cold.

Babies are born with a type of fat - so-called "brown fat" - that was thought not to exist in adults. The main job of this type of fat is to generate heat.

In brown fat cells, the electron transport chains in mitochondria are short-circuited. Instead of generating ATP, the energy from the proton difference across the inner membrane is used to to produce heat.

Brown fat has more mitochondria that can be used to generate heat. This also causes more calories to be burnt, which is one reason babies require so many calories per pound of weight.

We now know that adults who are exposed to cold develop brown fat as well. Some of their normal "white" fat also starts to act the same way. We refer to this is "beige" fat.

This beige or brown fat is rapidly lost when people move to hotter areas where it's seldom cold. These "snowbirds" find it difficult to go back to the cold areas from whence they came.

In cold conditions, cellular operations slow down. Proteins are made and broken down more slowly, and cells take longer to divide.

People exposed to mild cold for just a few days see improvement in insulin sensitivity. Muscle cells have more glucose transporters with which to absorb glucose from the blood and thus require less insulin.

Cold also reduces inflammation and levels of the stress hormone cortisol. Cold also spurs the generation of new mitochondria.

Heat is another stressor our species has had to deal with throughout its history. Heat is dangerous for cells because it wreaks havoc on many reactions and is therefore extremely dangerous.

However, our bodies react to short bouts of heat exposure by producing more of the chaperones and other substances that help deal with the danger.

Saunas are almost a way of life in Finland. Finns who take frequent saunas have dramatically lower rates of heart disease and dementia.

Cells produce special chaperones called heat shock proteins to help them deal with elevated temperatures. As with other hermetic stresses, this helps protect the cell not just from heat but a variety of other stresses.

We experience hypoxic (low oxygen) stress when we go into the mountains. There's simply less oxygen in the air for our cells to use.

In response to mild hypoxia, cells deactivate mTOR to reduce protein synthesis. This reduces the burden of misfolded proteins in neurons and other cells.

People who live in areas like Boulder, Colorado (elevation 5,000 feet or 1500 meters above sea level) live 2-3 years longer than flat-landers.

As with cold, hypoxia reduces the rate of protein synthesis and thus decreases the burden due to misfolded proteins. Hypoxia inhibits the master controller of protein synthesis - mTOR.

As strange as it may sound, even low levels of radiation can invoke a protective response.

Some doctors use low-dose radiation to treat Alzheimer's and Parkinson's although that is very controversial.

Radiation therapy at hot springs and even at the bottom of mine shafts is becoming as popular as it used to be before the development of the atomic bomb.

It's looking like just about any small, temporary stress can cause the body to generate a beneficial stress response.

Our species was designed to handle a variety of stresses, and to even get stronger because of them. Truly, what doesn't kill us makes us stronger.