Top Apps to Track Intermittent Fasting Windows
App guide
Ranked & compared
Zero is the cleanest dedicated fasting timer (one-tap start, 16:8/18:6/OMAD presets, Apple Health sync); Yazio combines fasting with full nutrition logging for GLP-1 users who need to track nutrient intake within eating windows; Fastic adds coaching content but its subscription price is unverified.
Intermittent fasting window tracking on GLP-1 medication involves a specific tension: the medication already suppresses appetite so strongly that eating windows can accidentally shorten further than intended, risking inadequate protein and micronutrient intake. Tracking fasting windows ensures eating windows stay wide enough to meet nutrient targets — the goal is a floor on eating frequency, not a ceiling. This guide compares Zero, Yazio, Fastic, and MyFitnessPal to help you choose the right tool for your needs.
This is general nutrition and wellness information, not medical advice. If you're on a weight-loss medication or managing a health condition, confirm specifics with your clinician.
What you're actually tracking
Intermittent fasting window tracking on GLP-1 medication involves a specific tension: the medication already suppresses appetite so strongly that eating windows can accidentally shorten further than intended, risking inadequate protein and micronutrient intake. Tracking fasting windows ensures eating windows stay wide enough to meet nutrient targets — the goal is a floor on eating frequency, not a ceiling.
How we evaluated them
Evaluated on: timer accuracy and protocol variety (16:8, 18:6, 5:2, OMAD); integration with nutrition tracking during eating windows; price transparency (noting Fastic's unverified pricing); platform availability; and specific relevance to GLP-1 users who need fasting windows that complement — not deepen — medication-driven appetite suppression.
The apps, side by side
No single app wins for everyone — each card calls out who it's genuinely best for, so you can pick on fit, not hype.
Zero
Free / Zero Plus $69.99/yr (monthly options also available)iOS / AndroidBest for: Simple fasting timer with educational content
- One-tap timer with 16:8, 18:6, and OMAD presets
- Apple Health sync
- Clean, friction-free interface
- Advanced analytics and AI food logging are Plus-only
- Occasional sync bugs reported
Yazio
Free / Pro $6.99/mo or $47.90/yriOS / AndroidBest for: Fasting-window tracking combined with full calorie and nutrient logging
- Built-in fasting timer for 16:8, 5:2, 6:1 protocols
- Free barcode scanning
- Nutrient tracking within eating windows
- Advanced fasting plans and full nutrient detail require Pro
Fastic
Free / Fastic Plus subscription UNVERIFIED (14-day refund guarantee)iOS / AndroidBest for: Guided fasting with habit and coaching content
- Fasting timer with water and step tracking
- Coaching and habit content
- Subscription price not published on official listing
- No Apple Watch app
MyFitnessPal
Free / Premium $19.99/mo or $79.99/yr (fasting tracking is Premium-gated)iOS / Android / WebBest for: Fasting tracking integrated with a complete nutrition log
- Fasting timer tied directly to nutrition data
- Largest food database (20.5M+ foods)
- Fasting feature is Premium-gated
Intermittent Fasting + GLP-1: Do They Combine Well?
Intermittent fasting and GLP-1 medications both reduce how often you eat — and that overlap is exactly where the risk hides. Stacking a restrictive eating window on top of medication-driven appetite suppression can push daily intake below the minimum needed to preserve muscle and meet micronutrient needs.
The theoretical appeal is straightforward: both tools reduce total energy intake by limiting eating opportunities. But GLP-1 receptor agonists like semaglutide and tirzepatide already delay gastric emptying and suppress hunger signals so effectively that many users struggle to eat enough even without time restrictions. Adding a short eating window can turn an already-low appetite into a genuine nutritional deficit.
The 2025 multi-society Advisory on obesity management emphasizes that during active weight reduction, protein intake should remain at 1.2 to 1.6 grams per kilogram of body weight per day to minimize lean mass loss. For a 75-kilogram person, that means 90 to 120 grams of protein daily — a target that becomes progressively harder to hit as the eating window shrinks.
The practical framing is this: use intermittent fasting as a structure for when you eat, not as a tool to eat even less. The medication already handles appetite reduction. The fasting schedule should create a predictable rhythm that makes it easier to plan and consume adequate nutrition, not a narrower window that compounds the medication's effects. A 16:8 protocol with an 8-hour eating window is generally safer than 18:6 or OMAD for GLP-1 users with high protein targets.
Bottom line
IF and GLP-1 can coexist, but the meal window needs to be long enough to fit 1.2–1.6 g/kg/day protein — 16:8 is generally safer than 18:6 or OMAD for GLP-1 users with high protein targets.
The 4 Best Apps for Tracking Fasting Windows
The right fasting app depends on whether you need a simple timer, a combined fasting-and-nutrition tracker, or coaching content. For GLP-1 users specifically, the ability to track what happens inside the eating window matters more than the fasting timer itself.
Zero is the best dedicated fasting timer. Its one-tap start, clean interface, and built-in presets for 16:8, 18:6, and OMAD make it the most frictionless option. The free tier covers core timer functions and Apple Health sync, while Zero Plus at $69.99 per year adds advanced analytics and AI food logging. Occasional sync bugs have been reported, but the overall experience is polished and reliable.
Yazio is the best combined fasting and nutrition app, and the strongest recommendation for GLP-1 users. Its free tier includes a fasting timer for 16:8, 5:2, and 6:1 protocols alongside barcode scanning and nutrient tracking within eating windows. The Pro version at $6.99 per month or $47.90 per year unlocks advanced fasting plans and full nutrient detail. Being able to see both your fasting window and your protein intake in one app eliminates the need to cross-reference two tools.
Fastic takes a coaching-led approach with guided fasting plans, habit content, and water and step tracking built in. The free tier covers the timer and basic tracking, while Fastic Plus adds the coaching library. The subscription price was not published on its official listing at research time, which is a transparency concern. It also lacks an Apple Watch app, which may matter for users who want wrist-based notifications.
MyFitnessPal offers fasting tracking as a Premium-gated feature tied to its massive food database of over 20.5 million foods. At $19.99 per month or $79.99 per year for Premium, it is the most expensive option, but it makes sense if you are already deeply embedded in the MyFitnessPal ecosystem and want fasting data layered on top of your existing nutrition log without switching apps.
Bottom line
Zero is the best pure fasting timer; Yazio is the best combined fasting + nutrition app, especially for GLP-1 users who need to track protein within eating windows.
16:8 vs. 18:6 vs. OMAD: Choosing a Window That Supports Protein Targets
The three most common intermittent fasting protocols create very different conditions for meeting protein needs on GLP-1 medication. The math is straightforward: the shorter the eating window, the fewer opportunities to consume adequate protein when appetite is already suppressed.
A 16:8 protocol provides an 8-hour eating window, which can realistically accommodate three to four small, protein-forward meals or snacks. For a 75-kilogram person targeting 120 grams of protein daily, that means roughly 30 to 40 grams of protein per eating occasion — achievable with a chicken breast, a protein shake, Greek yogurt with nuts, and a serving of fish across the day. This is the most viable structure for GLP-1 users.
An 18:6 protocol compresses eating into 6 hours, typically fitting two to three meals. Hitting 120 grams of protein now requires 40 to 60 grams per meal, which is harder when appetite is low. It is possible with deliberate planning — larger portions of lean protein at each sitting — but leaves less room for error if nausea or early satiety cuts a meal short.
OMAD, or One Meal A Day, is a 23:1 protocol that compresses all eating into a single one-hour window. Consuming 100 to 150 grams of protein in one meal while on a GLP-1 medication is unrealistic for most people. The stomach's reduced emptying rate and suppressed hunger make it physically uncomfortable to eat that volume in one sitting. OMAD is the highest-risk protocol for GLP-1 users and is not recommended without close medical supervision and a clear plan for meeting nutrient targets.
Bottom line
A 1.6 g/kg protein target for a 75 kg person requires 120 g of protein per day — hitting that in one OMAD meal while on GLP-1 is unrealistic for most people; 16:8 with 3–4 small protein-forward meals is the more viable structure.
Tracking Nutrients Within the Eating Window: The Case for Yazio Over Zero
A fasting timer tells you when you ate, but not whether you ate enough. On GLP-1 medication, the more important question is usually whether your eating window actually provided adequate protein, fiber, and micronutrients — not whether you fasted long enough.
Zero excels as a timer but does not track nutrition. You can log a perfect 16:8 fast and still have consumed only 40 grams of protein across the entire eating window, putting you at risk for muscle loss. The timer confirms compliance with the fasting protocol but provides no feedback on the quality or quantity of what you ate during the window.
Yazio solves this by linking fasting-window timing directly to the food log. When you open the app, you see both your current fasting status and your nutrient intake for the day. After breaking your fast, every logged food contributes to protein, fiber, and calorie totals that sit alongside your fasting timer. This integrated view makes it immediately obvious if your eating window is long enough to support your nutrition goals.
If you prefer Zero's timer but still need nutrition tracking, a free alternative is to pair Zero with Cronometer. Zero handles the fasting timer and Apple Health sync, while Cronometer provides detailed nutrient breakdowns including protein, fiber, and micronutrients. The downside is managing two apps, but the combination is powerful and the free tiers of both are sufficient for most users.
Bottom line
A fasting timer is only half the information you need — pair it with a nutrition log to confirm your eating window hit protein and fiber targets, not just to confirm you fasted long enough.
Common Mistakes When Combining IF Tracking With GLP-1 Medication
Most fasting-tracking mistakes on GLP-1 come from treating the fasting window as the goal rather than the eating window. The medication already guarantees reduced intake — the tracking should protect nutritional adequacy, not push restriction further.
The first mistake is choosing a fasting protocol based on weight-loss speed rather than protein feasibility. OMAD and 18:6 sound more aggressive and therefore more effective, but on GLP-1 they often backfire by making it impossible to eat enough protein. The protocol that supports consistent, adequate nutrition will outperform the one that maximizes fasting hours.
The second mistake is not adjusting the window length when nausea or early satiety shortens meals further. GLP-1 side effects can make eating uncomfortable, especially in the first few months or after dose increases. If you planned a 6-hour eating window but nausea means you can only manage two small meals, extending the window to 8 or even 10 hours is the right call — not forcing yourself to fast longer.
The third mistake is tracking the fast but not what is eaten during the window. A perfect fasting streak means nothing if your protein intake is half of what it should be. If you are logging your fasting windows but not your nutrition inside them, you are tracking the wrong thing on GLP-1 — the gap is usually protein, not fasting duration.
The fourth mistake is using intermittent fasting to eat less when GLP-1 already guarantees less. The medication reduces appetite and caloric intake on its own. Adding a restrictive eating window on top is redundant at best and harmful at worst. The fasting schedule should provide structure and predictability, not additional restriction. App alerts can help prevent each of these mistakes by reminding you to start eating, not just to stop.
Bottom line
If you're logging your fasting windows but not your nutrition inside them, you're tracking the wrong thing on GLP-1 — the gap is usually protein, not fasting duration.
What most pages leave out
Fastic's subscription price could not be verified from its official Google Play listing or official website at research time — the price is marked UNVERIFIED. Check the app store before subscribing. More broadly, there is no robust randomized-controlled-trial evidence that intermittent fasting adds meaningful weight-loss benefit on top of GLP-1 therapy; it may add structure but is not clinically required. Competitors rarely make this distinction.
We flag this so you can make an informed choice — not to scare you off.
❓Frequently Asked Questions
Zero is the best pure, frictionless fasting timer with one-tap start and presets for 16:8, 18:6, and OMAD. Yazio is the best combined fasting and nutrition app, ideal for GLP-1 users who need to track protein within eating windows. MyFitnessPal Premium works well if you're already using it for food logging and want to add fasting tracking without switching apps.
Yes, but the combination requires care. GLP-1 medications already suppress appetite significantly, and stacking a short eating window on top risks not eating enough protein to preserve muscle. A 16:8 protocol with an 8-hour eating window is generally safer than 18:6 or OMAD on these medications, as it provides more time to spread out protein intake across multiple small meals.
Zero has a usable free tier that includes the core fasting timer, protocol presets, and basic progress tracking. Zero Plus costs $69.99 per year and adds advanced analytics, AI food logging, and deeper educational content. The free version is sufficient for most people who just need a reliable timer.
Your fasting window should be long enough that your eating window fits your full protein target. For most GLP-1 users aiming for 1.2 to 1.6 grams of protein per kilogram of body weight, a 16:8 window with an 8-hour eating period is safer than 18:6 or OMAD. A shorter eating window makes it harder to consume adequate protein when appetite is already suppressed.
Yes, Yazio includes a built-in fasting timer for 16:8, 5:2, and 6:1 protocols on its free tier. The free version also includes barcode scanning and basic nutrient tracking. Advanced fasting plans and full nutrient detail require the Pro version, which costs $6.99 per month or $47.90 per year.
OMAD stands for One Meal A Day, a 23:1 fasting protocol that compresses all eating into a single meal within a one-hour window. It is the most extreme common intermittent fasting protocol and the hardest to pair with adequate protein intake on GLP-1 medications, since consuming 100 to 150 grams of protein in one sitting is unrealistic for most people with suppressed appetite.
Fastic's subscription price was not published on its official listing at research time. The app offers a free tier with basic fasting timer, water tracking, and step tracking, while Fastic Plus unlocks coaching content and additional features. Check the current price in the App Store or Google Play before subscribing — a 14-day refund guarantee is offered.
Tracking adds structure and prevents eating-window drift, which can support behavioral consistency. However, there is no strong randomized-controlled-trial evidence that adding intermittent fasting to GLP-1 therapy accelerates weight loss meaningfully. The main benefit is creating a predictable routine rather than an additional metabolic advantage.
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Read moreOn a GLP-1, or thinking about one?
Eating well is the foundation. For some people, a GLP-1 medication is the tool that finally makes appetite manageable.Curex connects you with licensed clinicians for compounded GLP-1 medications, if it's right for you.
- Compounded semaglutide from $49/mo, tirzepatide from $149/mo
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- Delivered to your door — no in-person clinic required
This content is for general informational purposes only and is not medical or nutritional advice, a diagnosis, or a substitute for professional judgment. It does not account for your health, medications, or goals, and nutrition information changes over time. Always talk with a qualified clinician or dietitian before making significant changes to your diet, supplements, or medications. Curex offers compounded GLP-1 medications through licensed clinicians and does not sell or endorse the food or supplement reviewed on this page.