What Exercise Is Best? - The Truth

I'm gonna tell you the single best exercise to do. But first let me tell you about red light therapy. (It is starting to be promoted by people all over the place and by every biohacker that will sell any and every half truth under the sun.)
I think red light therapy is a step in the right direction as it draws attention to light but of coarse has its issues. Red light therapy shows the benefits of red light to the body and the benefits are many. 

Relative to todays topic I'll only pick two 
Fat loss and testosterone boosting. 

Both of these quotes are from the Joov web site-

Joov fat loss claims 
"How Does Light Therapy Work to Reduce Fat?
Clinical Research Shows Light Therapy’s Potential for Increasing TestosteroneMedical scientists have been studying the effects of natural light on testosterone production for almost a century. Research over the last decade, and especially the last few years, has been even more illuminating and given the medical community more concrete reasons to believe in light therapy’s potential for increasing male testosterone. 

"Italian Pilot Study: A 2016 randomized, placebo-controlled pilot study conducted by the University of Siena in Italy evaluated 38 men with a diagnosed low sexual desire. Researchers measured their testosterone levels and separated the men into two groups, with one group receiving a clinical dose of light therapy in the early mornings. In addition to higher sexual satisfaction, the men in the group treated with more light saw their T-levels rise significantly. The control group did not see testosterone rises, but the active light therapy group showed a huge increase from about 2.1 ng/ml to 3.6 ng/ml in just 2 weeks. [2] "

​If you understand that red light helps with fat loss and testosterone then let me share a secret with you. 
In nature blue light is offset by red light. Guess what blue light does.......fat gain and testosterone decrease. Yup the opposite of red light therapy is blue light toxicity. Kind of makes everyone at the gym look silly.  
Any benefit from red light can be flipped backwards to know what blue light from your screens over head lights and the rest is doing.

So back to the question what exercise is best. Any motion at all done under natural light. Far better to take a walk in nature than to go break your body down under lights that cause fat gain and test decreases. 
I could go on and on about the science here but I wanna keep it simple. Movement out doors is the answer....any movement.

Whats my problem with Joov? On there adds they say 20 minutes is equivalent to several hours in the sun. If you understand that sun is expressed on a time spectrum and communicates time then you know a fixed light source from an a/c wall plug is no replacement for the sun. But it is a step in the right direction. The more benefit you get from red light therapy the more natural light you need to reset the circadian rhythms. Joov will not help you with this...in fact it may cause even more biochemical circadian confusion as  in the long term even if it expresses better chemistry than blue light. (questions the sales people aren't asking or don't wanna loose the pay check) 
Not my quote but saw it yesterday 
"you can't out nature, nature" 
Hint no ones natural environment is pure blue or pure red light. Neither is the solution.