How many calories can a 290 pound man eat a day if he wants to lose 50 pounds in 3 months?

Based on the formulation of the question, I assume that he's a 250-lb man with 50 lb of fat. Fat cells require virtually zero maintenance calories so he's only maintaining his target weight. If he's a reasonably young, reasonably active man with a reasonably healthy metabolism, his maintenance diet is approximately 3,000 calories per day. (I'm not getting out nutritional tables and a calculator, so my figures are probably only accurate to plus or minus 20%, but then so are most diets. ^_^) Every pound of fat represents 3,000 calories, so in order to lose 50 pounds he needs to reduce his intake by 150,000 calories over ninety days, which is between 1,500 and 1,600 calories per day. Subtracting that from his maintenance quote of 3,000 calories, we calculate his weight-loss diet at a little less than 1,500 calories per day. He'll have no trouble getting enough vitamins, minerals and other nutrients at that level of consumption, assuming he knows his way around the vitamin store and has some basic knowledge of nutrition, for example regarding fat-soluble vitamins and calcium-magnesium balance. However, he'll be very hungry. His body will metabolize his stored fat but that does not provide the same satiated feeling as metabolizing a good meal. Some people suggest that he'll have another, more serious long-term problem. They point to our fundamental nature as hunter-gatherers from an era when there was never enough of a food surplus to survive a serious famine. They point to people who have gone on crash diets and discovered afterward that their maintenance diet was 200-400 calories lower than it used to be... even after gaining the weight back. (I know someone that happened to but I don't know how prevalent it actually is.) Your Stone Age body goes into "famine mode" when it doesn't get what it considers enough to eat, and becomes more efficient at making do on what it has. According to this hypothesis and anecdotal evidence, this man will lose his nervous tics, he'll sleep more, he'll be less active and more efficient in the activities he does perform, and he'll find his food more thoroughly digested. And when the diet is over, his body might remain more efficient, preparing itself for the next famine. His new maintenance diet may be only 2,600 calories so he'll have a harder time maintaining his target weight. I don't know if this reasoning is correct but I have seen the phenomenon up close and it isn't pretty: a 180-lb person who can now gain weight on a 1200-calorie diet. It's suggested that the healthiest approach to weight loss is to attempt to lose no more than two pounds per month, which reduces your intake by 200 calories per day. That will not (according to the hypothesis) scare your body into famine mode. And in addition, since it will take you longer to lose the weight and you won't be starving yourself, you'll have a better chance of adapting to a lifelong lower-calorie diet. In any case, reducing his daily intake by 1,500 calories does not sound pleasant or healthy, not to mention whether he has the will power to endure the very real discomfort and keep it up for three months. This man will probably run out to the nearest McDonalds as soon as the event he lost his weight for is behind him.