Complex sentence: Like Orson Welles, he had a history of weight fluctuations through his career which, by and large, he attributed to his years of stress-related overeating followed by compensatory dieting.
Split into simpler sentences: Like Orson Welles, he had a history of weight fluctuations through his career. By and large, he attributed to his years of stress-related overeating followed by compensatory dieting.