LMGTFY: "base metabolic rate calculator"

gives you a few calculators that estimate your resting energy burn rate. Each human will be slightly different being noisy systems. Add in an entire lifestyle of different potential variations and you get a good feel that this is a very fuzzy estimate.

The first one on google gave me 1818kCal a day. You can look at the equation that got to that.

CICO is a close enough approximation to use for dieting. Dieting systems usually do what they do based on the assumption of CICO. given CICO if you also only eat blueberries you wont be very hungry or similar.

I believe the Shangri-la diet works in an interesting way around disconnecting calories with pleasure reward.

Most diets work if you can stick to them. Different diets might sound like they are selling the "what you eat" part, but in reality they are usually selling the "you can stick to it" part disguised as the "what you eat" part.

If you also look into the energy burnt during say; an hour of running, an hour of walking, and an hour of sleeping. You can get a sense of the scale of how much exercise impacts weight loss (hint: not much).

This can also be reasoned from first CICO principles that you can eat more calories in 5 minutes than you can burn in 5 hours running a marathon. (You can out eat your exercise routine and more effective interventions will involve diet than just exercise, but of course both together is best.)

As a final note: There will always be another birthday cake.