I haven't gone full keto but have lost body fat since last year and kept it off just by cutting way back on the beer. That's the single biggest change in my diet. I went from 1-3 beers a day most days, to 2-3 a month with dinner after group rides.
I'm 5'11", have dropped from 160-165 lbs, to 150 and have held it there for several months. And I could lose another 3-5 lbs of flab around my belly and small of the back over the kidneys. If I really wanted to. Which I don't. I'd need to cut out almost all sugar to lose the last few lbs. I'm not in competition for anything so I'm not that motivated.
I've cut back on some junk carbs but still use sugar and creamer in my coffee, usually 2-3 cups a day. I like Dunkin Donuts sweetened creamer.
And while I've cut back on sweets at home, I do occasionally indulge in a donut after a physical therapy session, which includes a short but intense round trip bike ride -- 3 miles of roller coaster and traffic sprints both directions.
Only difference I've noticed is that I'm as fast as I was before the weight loss, despite some injuries and illnesses. My power is actually down, but I'm faster on climbs. If I can keep the weight down as I regain strength, it might translate to being faster and having better endurance. But at 61 I've had to learn to be patient. Everything takes longer, including recovery.