| | Water Fasting

What to eat first when breaking a fast?

Do people have a preferred thing when ending their fast? I try to eat something proteiny, based on what I've read and how it feels, but I don't know if there's any actual data on this. Here's why I ask: Few days ago was Halloween, and I was out with the kids doing Trick or Treating in a group thing. I had a nice home-made pasta dinner at home planned for our family, but the kids wanted to stay out later and later. It was close to dinner when the other parents decided we should all get dinner at a kid-friendly restaurant to end the day. It was a school night, so I figured it would be a quick bite, and my family really wanted to tag along, so I said *okay* and declined to order for myself. But the other parents, apparently starved for adult conversation, kept it going until it was nearly *my* bedtime so when I got back I just decided to skip dinner too and make it a surprise 36 hour fast. When I finally got around to making dinner the next day I made sure to break my fast with stuff that felt healthy, like some full-fat milk, a palm of peanuts, a bit of mozzarella cheese, and veggies. I wasn't sure if breaking my extra-long fast with my pre-planned pasta would feel bad but I didn't want to risk it. I also find I get full faster when I break my fast with a mix of protein, fat, and fiber. Does it actually matter though? Is there any data, or is it all personal preference and anecdotal stuff?

Answer

I tend to shift fast-absorbed carbs and sweet-tasting foods including fruit toward the end, primarily to tame my appetite and secondarily to avoid feeling lethargic after my meal. In terms of energy expenditure, as someone with decent glucose tolerance, I doubt that food ordering affects me significantly (the margin of significance for me is +/- 100 kcal/day, anything more subtle I will acknowledge but won’t generally stress about). I do notice differences in thermogenesis when protein specifically precedes anything else, but only when I’ve eaten to a considerable surplus for the day.

Metabolically, as someone on a carb-friendly diet, after 20-30 fasted hours I’m presumably on a “fuel mix” delivered mainly via glycogenolysis and lipolysis; ketogenesis is barely noticeable (depending on carb intake and activity over the past few days, I may or may not even get the classic tell-tales of acetone breath and metallic taste around that time, presence of which nonetheless doesn’t guarantee that cells have actually began metabolizing these byproducts of fat catabolism for energy) and gluconeogenesis should be elevated but not yet peaked. Maybe with ideal timing and macro splits I could encourage slightly greater energy expenditure, by “feeding” beta oxidation and gluconeogenesis to their peak capacity (if only I had a tangible numeric clue of their respective “ceilings”); then have a bunch of fiber to buy me a little bit of time; then, with some additional delay, carbs, hoping that by the time the latter get absorbed and turned into glucose, the system will already have cleared out most of the fat and protein toward ATP, such that, worst-case, the carbs go toward glycogen replenishment and no new fat gets synthesized or stored. Pragmatically, if there’s any merit to my layman’s thought process at all, I doubt that it would be more than literal grams of fat such painstaking fine-tuning would “buy” (i.e. waste) me.

Resources: