# Maximum fat loss and fat burning workouts?

There's a study based on data from the Minnesota Starvation experiment that says that the maximum rate of fat loss is about 31.4 calories of fat per body fat per day. So, If you are a 200lb man with 15% body fat, you have 30lbs of body fat and can afford a 900 calorie deficit per day which your fat stores can provide. But I don't understand how this fits in with low intensity exercise, which primarily uses energy from fat. For example, suppose that same person walks for 5 hours (suppose he's at an amusement park, mall, etc) and he burns 1200 calories, with 60% of it coming from fat. He burned 720 calories of fat, but that's not even considering a caloric deficit. What if he was at 10% bodyfat so he could burn at most 600 calories of fat per day?

Some problems with the study: -I read some articles that analyzed the study, and the subjects performed "moderate exercise" which doesn't tell me whether or not they did a weightlifting program to preserve muscle mass and urge more calories to be burned from fat.

-The subjects were fed food similar to what soldiers would eat in WWII, so bread, potatoes, other starchy foods that were low in protein. This would lead to muscle wasting, and potentially less fat burned.

-
My general idea was that the more you walk and the more exhausted you get from it, the less you're actually using fat for energy. Maybe that's because you're nearing the limits of fat utilisation. At the very least, it should be possible to push that limit by walking more often (and longer). I'm just guessing though, looking forward to answers from other people. – LarissaGodzilla May 6 '14 at 16:55
I do know this much: don't consider the body to fit the second law of thermodynamics very well. The problem is that the body has a bunch of interconnected systems, so simple math only gets you in the ballpark to a certain degree. The confounding factors you sited can affect the rate of fat loss as well. – Berin Loritsch May 6 '14 at 18:35
The full study will have the details of the "moderate exercise" protocol. It will most likely some sort of cardio based exercise like a treadmill. By the reading of the excerpt, it appears that once you exceed the maximum fat transfer rate the body starts consuming fat free mass to compensate. I can't say for sure without paying \$40 for the full text. – Berin Loritsch May 6 '14 at 18:40