Why fasted workouts make you second-guess your pre-workout
You've skipped breakfast, laced up, and you're standing over a scoop of powder wondering if it's about to quietly cancel the sixteen hours you just put in. The gym clock says it's time to train, your stomach says it's still fasting, and the question of whether pre-workout breaks a fast is suddenly more urgent than the workout itself. You want the energy without giving up the thing you were actually trying to do.
How Mr. Hyde's ingredients interact with a fast
Here's what's actually in the scoop that matters for a fast. The caffeine, 196 milligrams of it, carries no calories and doesn't ask your pancreas to do anything on its own, so from a strict calorie standpoint it's fine before a fasted lift. Beta-alanine and creatine behave the same way: they're not sugars, they just sit in muscle tissue and buffer fatigue or support ATP output. That's the easy two-thirds of this formula. The amino acids are the part that changes the answer. Free-form amino acids, even in small amounts, get picked up by your gut and can nudge insulin and mTOR activity, which is the actual biological definition of ending a fast, whether or not the label rounds the calories down to zero. So the honest split is this: if your fast is really about an eating window, skipping breakfast to control when you eat, the aminos here won't matter to your day. If your fast is specifically about triggering autophagy or keeping insulin flat for blood work, the amino acid content quietly ends that state the moment it hits your gut, label claims aside.
This isn't a question with one universal answer, it's a question about which kind of fast you actually signed up for. The caffeine and beta-alanine are fasting-friendly by any definition, the amino acids are not, no matter how the label rounds the numbers. Worth it if your fast is a schedule, not worth it if your fast is a biology experiment.
Who Mr. Hyde pre-workout fits, and who should skip it while fasting
Worth it if
- you fast mainly to control your eating window, not for strict autophagy
- you want caffeine and beta-alanine energy before a fasted workout
- a few grams of amino acids won't derail your daily goals
Skip it if
- you're fasting specifically for autophagy or insulin-flat blood work
- you want a genuinely zero-calorie, zero-stimulant pre-workout
- you're sensitive to 196mg of caffeine on an empty stomach
Not for anyone fasting strictly for autophagy or a clean insulin response.
Mr. Hyde pre-workout review: is it worth it if you're fasting
If you fast mainly to control when you eat and you want real energy for an early workout, this is a quiet yes, use it and don't worry about the aminos. If you're fasting for strict metabolic reasons like autophagy or a fasting blood panel, skip it and reach for black coffee instead, that's the actual zero-calorie, zero-insulin option.
The gap between a rumbling stomach at six a.m. and a solid set of squats is the real problem here, and this closes it without adding a meal. On day one, you scoop, wait fifteen minutes, and the sluggishness that usually kills fasted workouts just doesn't show up. A very large number of buyers describe steady energy without a jittery crash, though a smaller share find the sweetness heavy-handed or notice their stomach isn't thrilled about training empty, worth knowing before you make it a daily habit.
Amazon shoppers rate it 4.3 out of 5 across 14,500 ratings. That is their number, not ours.
This is a product review, not medical advice. We research how products work and whether they earn their price; we don't test them clinically and nothing here is a treatment recommendation. For anything that affects your health, talk to a qualified professional first.
Before you go
Can you have pre-workout when intermittent fasting?
You can, if your goal is just controlling your eating window, since the caffeine and most ingredients carry no meaningful calories; the amino acids are the exception that can end a strict metabolic fast.
Will 5 calories break a fast?
Technically yes if you're fasting for autophagy or insulin control, since even a few calories or amino acids can trigger a metabolic response, though it won't matter if you're just fasting on a clock.
Will C4 pre-workout break my fast?
Most C4 formulas share the same issue as Mr. Hyde: the caffeine is fine, but any added amino acids can end a strict fast even at low calories.
What pre-workout won't break my fast?
Plain caffeine alone, or black coffee, is the safest option if you need a completely fast-compliant boost with no amino acids or sweeteners involved.
By the numbers
Like 90% of the 171 health & personal care products we've reviewed, this one earns a conditional "worth it, but" — just 7% clear our unconditional top tier. All verdicts are published as open data in the Is It Worth It Reviews Verdict Dataset (CC BY 4.0).
Full spec sheet
| Product Dimensions | 3.5 x 3.5 x 4.25 inches; 7.6 ounces |
|---|---|
| Brand Name | ProSupps |
| Primary Supplement Type | Pre-Workout |
| Item Form | Powder |
| Product Benefits | Energy & Focus Management, Pumps, Endurance, Blood Flow, Muscle Strength & Growth, Circ… |
| Age Range Description | Adult |
| Dosage Form | Powder |
| Model Name | See packaging |
