I have always intuitively felt that there was a relation between sunlight and weight.

When I live in California and am outdoors in the sun much of the time, I weigh approx. 16 lbs. (8 kg) less than I do when I live in Scandinavia and am covered up in tons of clothes to stay warm and the sun is quite limited during the Winter months.

Now, granted, I am pretty active in California - hiking, biking, swimming, skiing etc. but I never ever work out consciously. On the contrary, I do work out when I am in Scandinavia. Obviously this is kinda comparing apples to oranges, cos there are many variables.

However, I notice the most drastic weight-changing results when I:

1) Sleep

2) Get lots of daily sunlight on my body

Everything else is secondary.

Now there’s a study showing that this is exactly true (funny how we need science to prove reality, but hey, that’s how it is with these things).

In the study researchers found that the white unhealthy type of fat cells shrink under sun’s blue light. This breakthrough helps explain why we tend to pack on the pounds in winter regardless of no change in diet/activity. And this may very well lead to light-based treatments for obesity and other related issues like diabetes.

Read the full study here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5703708/