JSON.fit vs MyFitnessPal vs MacroFactor vs Hevy

There are a lot of fitness apps in 2026. This is an honest look at four of them — what each does well, where each falls short, and who each one is actually for. One of them is ours, so take this with appropriate skepticism — but we'll try to be fair.

The quick version

• MyFitnessPal — best free food database, worst premium value
• MacroFactor — best adaptive nutrition coaching, expensive long-term
• Hevy — best free workout logger with social features
• JSON.fit — best value if you already use AI, completely different model

MyFitnessPal

MyFitnessPal is the app everyone knows. It's been around since 2005 and has the largest food database of any nutrition tracker. For people who just want to log calories and macros, the free tier still works — but it's gotten significantly more limited over the years as features have moved behind the paywall.

The biggest issue is accuracy. Because the food database is largely user-submitted, entries are often wrong — duplicate items, incorrect macros, outdated information. If you're serious about hitting your macro targets, this matters.

Best for: People who just want basic calorie logging with the biggest food database, especially outside English-speaking countries where other apps have limited coverage.

MacroFactor

MacroFactor is the gold standard for adaptive nutrition tracking. Built by Greg Nuckols (one of the most respected researchers in fitness), it uses your daily weigh-ins and food logs to calculate your actual metabolic rate and adjust your calorie and macro targets week by week. It's genuinely impressive technology.

The downside is cost. At $79/year (or $12/month), it's a significant ongoing expense. And it only handles nutrition — if you want workout tracking too, MacroFactor Workouts is an additional $72/year, or $90/year for both bundled. Over two years, you're looking at $160–180.

Best for: People who are serious about body recomposition and want data-driven, adaptive nutrition coaching. Worth the subscription if nutrition tracking is your primary focus and you'll use it consistently for months.

Hevy

Hevy has quickly become the most popular workout logging app, and for good reason. The free tier is genuinely generous — you can log workouts, create routines, and track progress without paying. The UI is polished and the social features add a fun community element.

Where Hevy falls short is that it's purely a logger. It doesn't generate programs for you — you either build your own or follow a template. And there's no nutrition tracking at all, so you'd need a separate app for that.

Best for: People who already have a workout program and just want a clean, free way to log their sessions. Great if you enjoy the social/community aspect.

JSON.fit

This is our app, so we'll be transparent about the tradeoffs. JSON.fit takes a fundamentally different approach: instead of charging you monthly to use AI on our servers, we build the prompt and you use your own AI to generate the plan. This means workouts are free forever and nutrition is a one-time $9.99 purchase.

The tradeoff is that there's an extra step in the workflow. You copy a prompt into your AI, wait for it to generate the plan, then paste the JSON back into the app. Generation time depends on complexity — shorter programs are quick, while detailed multi-week plans with specific macros, pantry ingredients, and meal prep take longer as the AI works through more data. But once the JSON is created, it imports into the app in under a second. Whether that tradeoff is worth saving $10–20/month is a personal decision.

The upside is flexibility. Because you're talking directly to the AI, you can ask for adjustments in plain language. "I want more hamstring volume." "Replace all dairy." "Make it work with just dumbbells." Then re-import. With locked-in apps, you're limited to whatever customisation options they've built into their interface.

Best for: People who already use ChatGPT, Claude, or Gemini and want AI-generated workout and nutrition plans without another monthly subscription. Best value proposition of any fitness app if you're comfortable with the BYO AI workflow.

So which one should you use?

There's no single "best" fitness app — it depends entirely on what you need and what you're willing to pay. We built JSON.fit because we believed the subscription model for AI fitness was broken. But we also recognise that other apps do certain things better than we do, and we've tried to be honest about that here.