The claimWhat Jimmy actually said
Kimmel described the routine as starving himself two days a week, naming Monday and Thursday as his low-calorie days. He explained the rationale as surprising the body to keep it guessing. The pattern he describes is what is commonly called the 5:2 diet.
- maxim.com: Jimmy Kimmel in their own words
- Garegnani et al., Cochrane Database of Systematic Reviews, 2026, review of randomised trials concluded intermittent fasting may result in little to no difference in weight loss or quality of life versus regular dietary advice.
- Cioffi et al., Journal of Translational Medicine, 2018, meta-analysis of 11 randomised controlled trials found intermittent energy restriction produced weight loss comparable to continuous energy restriction.
Why it mattersWhy this matters for longevity
The evidence base here is randomised trials rather than observational data, which is unusually strong ground for a diet question.
If two approaches produce the same result, the one a person can actually sustain is the deciding factor, not the one with the better story.
Very low calorie days can be poorly suited to people on glucose-lowering medication, people who are pregnant, and anyone with a history of disordered eating.
The evidenceWhat the science says
Cioffi's meta-analysis of 11 randomised controlled trials compared intermittent energy restriction against continuous restriction and found comparable weight loss, with a difference of about 0.6 kg that was not statistically significant. A slight reduction in fasting insulin appeared with the intermittent approach, though the authors questioned its clinical relevance. The 2026 Cochrane review by Garegnani and colleagues concluded that intermittent fasting may result in little to no difference in weight loss or quality of life compared with regular dietary advice, and that evidence on adverse events is very uncertain.
The evidence does not support Kimmel's stated mechanism. Nothing in these trials shows that varying intake surprises the metabolism or produces an effect beyond the calorie deficit itself; the weight loss is explained by eating less across the week. The trials also ran mostly 8 to 24 weeks, so long-term maintenance, which is the part that actually determines outcomes, remains poorly measured. Kimmel's own description of eating freely on the other five days is precisely the behaviour that can erase a two-day deficit.
TakeawayThe honest takeaway
The practical lesson
If two low-calorie days a week is easier for you to stick to than cutting a little every day, that is a legitimate reason to choose it, and the only one the evidence offers.
RelatedRelated habits
Each of these is a habit you can build on its own. Explore them through the Topics index.
SupplementsThe supplement angle: Protein and micronutrients
Support a habit, do not replace one
Days at 500 calories leave limited room for protein and for vitamins and minerals, so the weekly average is what needs to hold up rather than any single day. Anyone on medication that affects blood glucose should speak to a clinician before adopting very low calorie days.
Supplements can support good habits. They do not replace sleep, movement, nutrition, or medical care. Talk with your healthcare provider before starting anything new.
This is educational commentary, not medical advice, and does not imply that Jimmy Kimmel endorses, is affiliated with, or uses Winning Longevity or any product. We critique the claim and the evidence, not the person. Any direct quote is a placeholder until sourced. Talk with a qualified healthcare provider before changing your routine. See our health disclaimer.
