The main issue is body composition (see the body fat calculator for more). Calorie expenditure will vary depending on the ratio of body fat to muscle or lean mass. NOTE that as our bodies adapt to exercise and our body composition changes - so will the amount of Calories burned.
The definition of a throttle is a valve that controls the fluid flow. An example of a throttle is a car part that controls how fuel moves through the system. Throttle is defined as to control the speed of an engine or the flow of fuel in an engine, or to hold down or choke.
The throttle body regulates the air flow that goes into the engine. It is used in conjunction with a fuel injection system. A cable connects the accelerator to the throttle. When the accelerator is pressed, the throttle opens, allowing for more air into the intake system. The throttle body spacer permits more air than usual to go into the engine.