Catabolic reactions break down complex chemicals into simpler ones and are associated with energy release. Anabolic processes build complex molecules out of simpler ones and require energy. The change in free energy of a reaction can be negative (releases energy, exergonic) or positive (consumes energy, endergonic).

Anabolic pathway: small molecules are assembled into larger ones. Energy is typically required. Catabolic pathway: large molecules are broken down into small ones. Energy is typically released.

Anabolic reactions require an input of energy to synthesize complex molecules from simpler ones. Other energy-storing molecules, such as fats, are also broken down through similar catabolic reactions to release energy and make ATP (Figure 1).

Remember that anabolic cellular pathways require energy to synthesize complex molecules from simpler ones and catabolic pathways release energy when complex molecules are broken down. The fact that energy can be released by the breakdown of certain chemical bonds implies that those bonds have potential energy.

Physical exercise involves both anabolic and catabolic processes. Body cells break down sugars to provide ATP to do the work necessary for exercise, such as muscle contractions. This is catabolism. Muscle cells also must repair muscle tissue damaged by exercise by building new muscle.

Catabolic Reactions. Catabolic reactions break down large organic molecules into smaller molecules, releasing the energy contained in the chemical bonds. These energy releases (conversions) are not 100 percent efficient. It is the first bond that catabolic enzymes break when cells require energy to do work.

Anabolic and catabolic pathways: Anabolic pathways are those that require energy to synthesize larger molecules. Catabolic pathways are those that generate energy by breaking down larger molecules. Both types of pathways are required for maintaining the cell’s energy balance.

Early fasting state Around 3–4 hours after eating, your body transitions into the early fasting state, which lasts until around 18 hours after eating.

Well, we all know that any diet takes some time to show results. The same is with intermittent fasting. Experts suggest that a person needs to follow the basic rules for at least 10 weeks to witness some positive results.

Fasting for 16 hours a day, leaving an eating window of 8 hours, is called the 16:8 method or the Leangains diet. During the 16:8 diet, men fast for 16 hours each day, and women fast for 14 hours.