Earlier quoted context omitted.
From the paper "Replacing one hour of rest with exercise that raises the metabolic rate to seven times that of resting by, for example, jogging, removes an additional 39 g of carbon from the body, raising the total by about 20% to 240 g. For comparison, a single 100 g muffin represents about 20% of an average person’s total daily energy requirement. Physical activity as a weight loss strategy is, therefore, easily fo…
200g are what would be "breathed out" in one hour without exercise? So you can only increase your "burn rate" by 20%?
You can definitely increase your burn rate by way more than 20% with heavy exercise. A Tour de France bicyclist will burn several thousand calories (4,000-7,000 depending on the stage and rider) in only about six hours. For comparison, a typical sedentary person will burn 2,000-2,500 calories per day. It can be physically difficult to eat enough at that rate, and riders lose a substantial amount of weight over the race. (A friend once told me about an endurance cyclist he knew who would eat a big bowl of cereal each morning, except instead of milk he'd use olive oil. Disgusting, but an effective way to get enough calories in.)
It's pretty tough for most of us to achieve anything like that much exercise, of course. Even Tour de France riders only do it for a few weeks at a time.