The fatty acid oxidation principle of recomposition
If you are like most people you follow the principle of “if it ain’t broke, don’t fix it”, which probably has most people successful in this sport wondering why on earth they would change a winning formula to take up IF. Well, because I firmly believe that it can shave time off your total diet, alongside making things easier. The reasoning is easy. When your body goes into acute energy stress, anabolic processes shut down and muscle and liver switch to systemic resources, meaning they switch to the bodies fat reserves to provide their energy. This initiates processes of lipolysis (the release of fat from fat cells) and fatty acid β-oxidation (the burning of fat for energy). However whenever you eat a meal, you will create an insulin and incretin response, and these hormones signal the body that there is new energy incoming, and initiates a number of anabolic processes to store the energy, in the process shutting down lipolysis and fatty acid oxidation. No more fat for fuel. That means the more meals you consume over a spread pattern, the more often you inhibit these processes, who need to be restarted each time after all the food has been processed. Now I have no time frame for these things, so I’m using a hypothetical number of 2 hours of inhibition for a meal (could be more, could be less, just using it to explain the math). If you eat 6 meals, well spread out, you will be inhibiting the use of fat for fuel for 6×2 hours = 12 hours. If you are eating 3 meals inside a 6 hour window, your maximum inhibition is 6h+2h = 8 hours. That means following an IF pattern you will spend 4 more hours burning fat as fuel than you would with a spread pattern. The fact that you do that also implies 4 hours of reduced protein catabolism. Now there is a need for amino acids, since on a hypo-caloric diet the majority of endogenous glucose production comes from gluconeogenesis rather than glycolysis, and in the fast your muscle will give up some protein, longer than in a spread pattern. But because fat is being used as the principle fuel source a lower amount per timeframe is being released because there is less need for endogenous glucose production. Combine that with what know of muscle storing increased amino acids beyond what they incorporate when you eat meals denser in protein than required (as you would, compressing the same amount of protein in just 6-8 hours), which would have a sparing effect on myofibrillar protein, and it’s easy to understand how an IF pattern will cause you to lose procentually more fat than muscle, shaving time off your diet to reach your goal and having a mild muscle sparing effect.
And despite all that, 99% of IF’ers don’t even know this.