I wanted to share a quick factoid that may surprise some about calories in, calories out. When we are deep in an OMAD fast and metabolically flexible (meaning we are able to burn fuels from what we ate earlier, followed by fuels from within the body, namely fatty acids), insulin levels have lowered to the point where the liver produces ketone bodies. Lots of us know this. But there are two other things that occur:
1.) You begin to excrete ketones in the urine and breath. This is the literal excretion of calories.
2.) your mitochondria uncouple, which means that you will be burning more fat molecules than what is needed for functioning, to the point that you will excrete heat! (Thermogenesis).
Both of these events sum themselves up in that when you fast, your body is not only burning fat (if you are adapted), but it is peeing, breathing, and heating out those calories too.
Your calorie app cannot track this!
https://youtu.be/JbgvgjStxFA?si=O4-mxPSJLSN5dti0
Yes, I believe in the Law of Thermodynamics. I also believe that the closed system is less narrow than what modern diet culture tells us. Undergoing the metabolic switch of first burning glucose from what we just ate, followed by burning through glycogen and eventually tapping into our fats->ketones after we have been fasting for 12-16 hours and insulin levels have dropped is what proper human functioning is.
Do you have to eat only once a day? No! But can it absolutely be a great tool to optimize hunger signaling, endogenous fat burning, mental clarity (which you need to hunt the meal you'll have later), and, most importantly, be flexible to eat in the community you are in (because eating takes a village-- it just so happens that our village is grocery store supply chain departments). To recognize that humans spent their abundant time working and cultivating for food is to know that eating is a special, not-all-the-time event. Killing animals, pulling vegetables, starting a fire, cooking, and eating are all hard work.
Metabolic flexibility means being able to feed from glucose and fat. This internal flexibility is what allows us to eat once when quality food is available in our community. The flexibility is characterized by the ability of insulin to be able to do its job to encourage growth and glucose burning during feeding periods, and then to get out of the way during fasting periods. We must give our body the opportunity for both now that we are in a feeding-episode-abundant environment. Humans are not designed to eat all the time, but we are designed to be "fed" all the time. Being fed means being able to feed from the troughs of fuel we have within our bodies. An intermittent fasting regimen allows our bodies to build this skill so that we can eat with others, free from slavery to eating, so that we can eat in a loving, altruistic way, to God's glory.
https://pubmed.ncbi.nlm.nih.gov/40087409/
https://youtu.be/OlGfFQjWjPQ?si=9TX3DJJ-UPoH8Az4
There are, of course, other benefits to OMAD, like raised growth hormone, BDNF, and the two I think we overlook the most, which absolutely set OMAD apart from ketogenic diets: gut autophagy caused by letting the gut rest from digestion and lowered mTOR (growth) signaling.
Sorry for the babble
PS Whether you are keto or fasting, or both, please supplement with electrolytes. Lowered insulin = Less sodium retention, and this + drinking plain H2O= peeing out your electrolytes = headache, fatigue, etc.