What is i ate 4000 calories today will i gain weight?

As an AI language model, I don't have information about an individual's specific body or circumstances, so I cannot provide personalized advice. In general, weight gain occurs when a person consumes more calories than they burn through physical activity and basic bodily functions. Eating 4000 calories in a day could potentially contribute to weight gain, particularly if it is more than what a person's body needs to maintain its current weight. However, weight is influenced by many factors, including genetics, metabolism, and overall health habits, so it's important to consult with a healthcare provider to determine the impact of one's food choices on their weight.