This is another recurrent question amongst people following a keto or low carb diet.
Fact is, there is no definitive answer, simply because it all depends on your goals. If you are obese or you have quite a lot of fat to lose, eating twice a day in a restricted window of time is often the best option in the long term, and one meal a day could be even better if your appetite is kept well under control during the day.
Eating fewer times, even better if in a short time frame, helps significantly with weight loss, and it’s recommended for the vast majority of the population: that means skipping breakfast (the most overrated meal ever) and eating lunch and dinner within 5-6 hours or less from each other.
Eating only one meal a day can be trickier, because for most people one meal, whatever big, isn’t enough to keep you satiated all day and therefore is a strategy that can be used for a limited period of time.
On the other end, three meals a day are best suited for athletes, and bodybuilders can bulk up much easily with four or five meals a day.