Earlier studies have suggested that people can burn up to 10 times basal metabolic rate for short bursts of activity. The metabolic ceiling represents the maximum number of calories that a body can actually burn. When competing in multi-day races, some of the athletes burned six to seven times their basal metabolic rate, or about 7,000 to 8,000 calories per day. They could not surpass the average metabolic ceiling of 2.5 times their basal metabolic rate in energy expenditure. It’s entirely possible that some exceptional individuals capable of exceeding the metabolic ceiling may have been missed.