When you reach your goal weight, you will need a maintenance plan. Returning to your old eating habits will have you regaining the weight you lost very quickly and waste all your work in adapting and following the Fast-5 diet. You’ve done the hard part, getting to your goal. Adjusting to steady-state maintenance is something you can fit individually to your lifestyle. You can maintain your Fast-5 plan indefinitely, and your break~fast and later consumption will balance your needs. In the unlikely event that you are continuing to lose weight beyond your desired point, increase your meal size, cut back on your fasting days, or lengthen your eating window. You may choose to fast only on weekdays or weekends, if that suits your schedule, but changing back and forth between fasting and non-fasting days is more difficult than keeping a consistent schedule. Tailor your schedule to what works best for you, and see the web site for more maintenance ideas. The human body, like all living things, is a biochemical engine. The machinery in living cells makes the burning of fuel a slow, multi-step sequence instead of the sudden explosive combustion that occurs in a mechanical engine. The summary of the biologic process yields the same chemical result as a mechanical engine: fuel is oxidized (burned) to produce energy, carbon dioxide, and water. Although fuels for mechanical engines (gasoline, Diesel fuel, kerosene) are chemical cousins of fats and edible oils, slight differences make the petroleum-based fuels toxic. In contrast, some mechanical engines can run on edible oils. The body engine’s combustion takes place in tiny components of cells called mitochondria. The cellular exhaust (carbon dioxide) dissolves in the bloodstream and is transported to the lungs and exhaled in the breath. The next breath takes in more oxygen to support the combustion going on in the mitochondria. The analogy of body engine and gasoline engine gets even more interesting. If you’ve ever started a lawn mower, you probably put the throttle in the choke position to start it. “Choke” means the engine’s getting a lot of fuel and very little oxygen (from the air). The engine starts well in this position, but for it to run smoothly, the throttle has to be moved off choke, reducing the fuel-to-oxygen ratio. If the mixture of air and fuel is right (conveniently termed “lean”), the engine generates maximum power and burns the gasoline cleanly, without producing much soot or sludge. If the fuel-air mixture is kept too rich (too much fuel for the oxygen available), partially burned fuel comes out in the exhaust as soot, and sludge builds up in the cylinders and valves, shortening the useful life of the engine. Mitochondria, the cylinders of the biologic engine, have the same outcome. Excess fuel promotes the production of damaging waste products (oxygen free radicals), which cause cell and DNA damage. The damage results in aging and according to a number of animal studies, shortens the useful life of the biologic engine/animal.