Sports Nutrition Fat Burners & Thermogenics: what Claude and GPT would buy

Two AI models chose on their own, with no web access. Nobody tested these products: this is what each one says, and how to check it.

They disagree: Claude chooses Transparent Labs and GPT chooses Nutricost

In Health & Household, Claude and GPT choose the same brand in 14 of 26 categories.

Claude Opus 5.5 · October 28, 2026

Transparent Labs Fat Burner (line)

It uses a fully disclosed label with no proprietary blend, so you know the caffeine dose, and the brand publishes third-party testing; most thermogenics offer neither.

Not for: People sensitive to caffeine, anyone pregnant or nursing, people with heart, blood pressure or anxiety conditions, and anyone on stimulant or MAOI medication.

GPT 6.1 Sol · November 10, 2026

Nutricost Caffeine (line)

A straightforward caffeine-only option without a proprietary stimulant blend; any weight-loss benefit is likely small.

Not for: Minors, pregnancy, caffeine sensitivity, heart conditions, or use with other stimulants.

Which one fits you

stimulant-free / evening use

Transparent Labs Fat Burner Stim-Free (line)

It gives the same transparent-label approach without caffeine, for people who already get enough from coffee or train late.

Not for: Anyone who wants the energy lift of a classic thermogenic.

alternate fully dosed option

Legion Phoenix (line)

It is a clinically referenced, fully disclosed formula that comes in caffeinated and caffeine-free versions.

Not for: Buyers looking for a cheap single-ingredient caffeine product.

Check before you buy

Label transparency. Every ingredient is listed with its own dose. Skip proprietary blends. With a blend you cannot know the caffeine or stimulant load or compare it with research doses.
Caffeine per serving. Count it toward a total daily intake of no more than about 400 mg from all sources for healthy adults. Caffeine is the ingredient with real evidence, and also the main cause of side effects such as jitters, insomnia and a fast heart rate.
Stimulant stacking. Be cautious with synephrine, yohimbine or higher-stimulant compounds combined with high caffeine. Stacked stimulants raise cardiovascular and anxiety risk without proportional benefit.
Third-party testing. Tested athletes should look for NSF Certified for Sport or Informed Sport. Weight-loss supplements are a category often affected by contamination and spiking.
Realistic expectations. Treat it as a small add-on to a calorie deficit, never a substitute. Even the best-evidenced ingredients produce only modest effects.

Where to find Transparent Labs Fat Burner

Transparent Labs

Shops seen in search results on November 6, 2026. A shop missing here may sell it too. Nothing was checked by a person.

Brands that matter

Transparent Labs: Disclosed doses, publishes testing, offers stim and stim-free versions.
Legion: Disclosed, research-referenced formulas.
NOW Foods: Sells single ingredients (green tea extract, caffeine), so you can build a simple stack yourself.

What to avoid

Proprietary blends that hide stimulant doses
Products listing DMAA, DMHA or other banned or unapproved stimulants
Stacking a fat burner with pre-workout and heavy coffee
Products promising specific pounds lost per week

Questions

Do fat burners actually work?

Caffeine and green tea catechins slightly raise energy expenditure, but the effect is small. A calorie deficit does nearly all the work.

All of Sports Nutrition Products