Why do I hit an afternoon energy slump on 16:8 intermittent fasting?

[Jonathan61]

I started a 16:8 intermittent fasting schedule six weeks ago to help manage my prediabetes and lose some weight, and while my blood sugar readings have improved, I'm hitting a major energy wall every afternoon around 3 PM. I work as a project manager, and this slump is killing my productivity during crucial meetings. I'm not sure if I should adjust my eating window to be earlier, change what I'm eating during my meals, or if this is just a temporary adaptation phase that I need to power through.

[Kenneth81]

You're not alone. A quick win is to shift your eating window earlier (for example 9:00–17:00 or 10:00–18:00) so you can have a balanced snack around 2:45–3:00 within the window. Build that snack around protein+fiber+a little fat (Greek yogurt with nuts, or a small cheese and fruit). Pair lunch with 25–40 g protein and high-fiber sides, stay hydrated, and see if the 3 PM dip eases after a week or two.

[LarryJR]

Two-week micro-experiment plan: A) move to 9–17; B) refine meals—bigger lunch with protein and fiber, lighter dinner; C) if you still crash, try a 14:10 window temporarily while you adapt. Track energy on a simple 1–5 scale and note meeting performance.

[StevenTJ]

Also consider meal timing around workouts or important meetings. A small, protein-rich snack around 2:30–3:00 can blunt the drop without breaking your fast too much if you still want a shorter window. For example, a protein shake or a handful of nuts and cheese in your eating window.

[JohnTM]

Be mindful of diabetes risk. With prediabetes, a too-long fasting state could affect energy; check with clinician if you have meds or if you see symptoms. If you have continuous glucose monitor data, look for patterns around meals and fasting.

[EdwardB]

Want a tailored plan? Share your current eating window, typical meals, daily meeting schedule, and whether you exercise; I’ll sketch a two-week plan you can test.