Intermittent Fasting: Early Surprises and Insights

I’ve completed 1.5 weeks of intermittent fasting (“IF”) at this point, and it’s led to some early insights into why the diet works along with its primary challenge. There have been some nice surprises along the way as well, including a nearly 10-lb weight loss in 5 days.

Let’s start with the surprises:

1) Rapid weight loss: I lost 5.5 lbs after 2 days and 9.5 lbs after 5 days, which was a great immediate feedback loop. I did have to re-calibrate a bit and start adding more calories into my day, which led to ending the week down only 6 after adjusting and adding more carbs at each meal. Headed into week 2, I expect to see another 4–5 lbs this week and am well on the way.

2) Hunger isn’t bad: After 1–2 days, my body got pretty used to it and I wasn’t that hungry at night. It was usually the worst at the end of each fast in the late morning (9 am), which was compounded by my early am workouts. I still haven’t figured out optimal timing for exercise, although my current thought is 1–2 hours into the eating window after the first meal. Will continue to test this out in weeks to come.

3) More natural energy: Almost immediately I had more natural energy and was sharper during the day. I dropped from what was a regular 5–6 cups of coffee per day down to 3, and plan to drop to 2 in weeks 2–3. During the first few days, I actually had huge energy spikes during the late evening where I was wired at 8–9 pm and required a hefty dose of melatonin to fall asleep.

Beyond those initial surprises, I’ve spent a good amount of thought in how to make this diet work long term, inclusive of why I think it works and challenges to long-term adoption. Here is a summary of those initial insights:

1) Discipline is the underlying key to success: This isn’t a novel take, but it became clear that if you’re instilling the discipline to only eat in an 8-hr window, you’re probably also going to use some discipline in food selection and amount. I naturally ate healthier and in more reasonable quantities during my eating windows, when compared to my normal eating habits. Additionally, it’s simply harder to overeat in an 8-hour window, which is another primary driver of the unexpected calorie restriction. Thus IF leads to naturally pulling two diet levers (time restriction and calorie restriction), which seems to be the primary driver of it’s success at least early on.

2) It’s not a social diet: IF doesn’t lend itself easily to socializing, especially late dinners and drinking. It’s even tougher for schedules like mine (eating window generally 9–5). To allow any sort of socialization, one would have to skip breakfast and move to the later shift (12–8, 2–10, etc.). From the research I’ve done, the most common long-term schedule is the later shift, with most recommending one large single meal in the evening with small snacking during other parts of the window. This does seem the most reasonable, and allows for some degree of socialization, so I’ll need to tinker with my schedule to get to this later shift.

3) IF feels very sustainable: Given I’m still only 1.5 weeks in, but IF feels very sustainable. Even if choosing to give in to social pressures on the weekend, I could definitely see using some kind of hybrid approach in perpetuity. My optimal “hybrid” version would be to maintain IF strictly 4–5 days per week and adjust time windows on 2–3 off days — 8 on / 16 off as core time constraints, with a few days of 10/14 as “off” days. This would keep to the spirit of the diet, and I imagine you can still reap some/most of the benefits. Even just doing IF 5 days a week seems very doable long term and a nice compromise over reversion to open eating.

I’m going to keep tinkering with the food schedule, workout timing and other variables, along with trying to integrate with some sort of social normalcy to test sustainability. I plan to report back after more substantial time on the diet, hopefully with some deeper insights. So stay tuned for that…