Fat is used to store energy. Carbohydrates.
Dehydrated foods can be more healthier and have less fat than other foods, but that depends on what dehydrated foods you are eating. The benefits of dehydrated foods is that they have a longer shelf life, weight a lot less, can be prepared in minutes, and with store is smaller compartments than regular food would.
Fresh vegetables and fruits are often low in fat. White meats contain less fat then red meats. When in your grocery store check the labels of the foods you are buying most products offer a low fat or fat free option. This is also a large list of low far foods that I came across. http://www.buzzle.com/articles/list-of-low-fat-foods.html
Foods which are rich in Carbohydrates and glucose (Sugar) provide energy. If you eat a lot of these and don't use that energy, your body will store it. Consume more energy thatnyour body needs, you're body will store it as fat, and you will gain weight.
foods that are high in moisture and in fat are more likely to be perishable
Foods such as fruits, vegetables, whole grain foods, and low fat or non fat dairy products, are naturally low in fat.
No fat in fat free foods, but the sugar and carbs left over that you don't burn as energy is stored as body fat.
In order to know this you will need to start reading labels on foods you consume. Many fat is stored by eating right before bed and eating many carbohydrates without burning them off. Fat cells are stored by eating unhealthy and/or consuming in too large of quantities.
why the exchange of fat-containing foods with fat-substitute-containing foods would not be ideal for a marathon runner
There are no "fat burning foods." Foods contain fat; they don't burn it. Exercise is what burns fat.
Foods high in fat.
They store the fat in their tails