One number decides whether this product is worth the money, and it is not the one on the front of the jar. Per 100 kcal, Professor Nutz gives you 17.5g of protein. Ordinary peanut butter gives you about 4.4g. That is roughly four times the protein for the same calories, and it is why this sits in my cupboard permanently rather than as a novelty.
MyCore Supplements is a partner brand. No commission is earned on anything here — see the partner disclosure. I bought this for years before the partnership existed.
Per 100 kcal, Against Everything Else in the Press
Grams-per-100g comparisons flatter whatever is driest. Calories are what you actually budget, so this is the comparison that matters.
| Food | Protein per 100 kcal |
|---|---|
| Professor Nutz low calorie peanut butter | 17.5 g |
| Philadelphia Protein soft cheese | 12.6 g |
| Ordinary smooth peanut butter (8 brands) | 4.3–4.5 g |
| Lotus Biscoff biscuit | 1.0 g |
The peanut butter figure is not one cherry-picked jar. Eight mainstream smooth peanut butters checked on Open Food Facts land between 4.3g and 4.5g of protein per 100 kcal — the category is remarkably consistent, because it is fundamentally a fat product with protein along for the ride.
Is the 40-Calorie Claim Real?
It sounds like nonsense, so I checked it rather than trusting it. The label declares, per 32g serving: 7g protein, 3g digested carbohydrate, 0g digested fat, 3g fibre, 40 kcal.
Run those macros through the standard Atwater factors — 4 kcal per gram of protein, 4 per gram of digestible carbohydrate, 9 per gram of fat — and you get exactly 40 kcal. The label is internally consistent. Plenty of "low calorie" products fail that test; this one does not.
How they get there is straightforward once you read the ingredients: dry roasted peanuts with most of the fat pressed out, then corn fibre and soluble tapioca fibre replacing the bulk, sweetened with erythritol, monk fruit and stevia. The same 32g of ordinary peanut butter is about 190 kcal. You are trading fat calories for fibre, and the texture reflects that — it is thicker and less oily than the real thing, which some people will not like.
The Study On Their Site: Read the Sample Size
Professor Nutz publish a study, and it is worth being straight about what it is.
It was a randomised, double-blind, placebo-controlled crossover trial run at the Applied Science and Performance Institute in Tampa: two 2-week intervention periods separated by a 4-week washout, measuring body composition by DXA and resting metabolic rate by indirect calorimetry. Regular peanut butter was associated with roughly 1kg of fat mass gain; the modified product with none. Published in IP Journal of Nutrition, Metabolism and Health Science, 2020.
Six people. Six healthy non-obese men, over two weeks each. That is not enough to establish that a food prevents fat gain, and a journal at that tier is not a substitute for sample size. The design is decent — crossover with a washout is the right shape — but the n is what it is.
None of that is a reason not to buy the jar. The reason to buy the jar is on the label: 40 kcal instead of 190 for the same spoon. That is a real, arithmetic-checkable difference that does not need a trial to justify it. The study is marketing, and treating it as more would be the same mistake the coupon sites make with their discount numbers.
What I Actually Do With It
Night-time, on a cut, when the sugar craving turns up and there is nothing in the day's budget for a dessert.
A 165g tub of Philadelphia Protein soft cheese, a 32g serving of Professor Nutz stirred through it, and two Lotus Biscoff biscuits crumbled in.
259 kcal and 25.9g of protein — 10g of protein per 100 kcal. It genuinely keeps you full, and it kills the sugar craving, which on a cut is the thing that actually ends diets rather than hunger itself.
I had this in my head as roughly 320 calories and 20g of protein. Running it properly, the protein is a good bit higher than I thought and the calories a bit lower. Worth doing the sums on your own regulars — mine were wrong in the direction of underselling it.
Two honest notes on that arithmetic. Philadelphia's protein figure comes from Open Food Facts rather than the tub in front of me, because protein is not on the front-of-pack panel — the energy figure I did verify, and the pack's 26 kcal per 30g matches the database's 87 kcal per 100g. And a Biscoff biscuit is taken as 7.8g, from a 250g pack of 32. If yours are the individually wrapped ones they are lighter, and the total drops slightly.
Building this into a day is easier with numbers in front of you: the free food tracker has the Irish products in it, and the TDEE calculator tells you what the budget is in the first place.
Flavours, and the One That Is Never in Stock
Six flavours are in the low calorie line, and I have had all of them:
- Original
- Birthday Butter
- Caramel Kiss
- Coconut Macaroon
- Cookie N Cream
- Prince of Pistachio
They are all genuinely nice, which is not a given in this category — most reduced-calorie spreads taste like the compromise they are.
Chocolate is my favourite and it has been out of stock a long time. Worth flagging one thing about it: MyCore list it as Professor Nutz Peanut Butter — Chocolate, without the "Low Calorie" that the other six carry. That looks like a different product line rather than a seventh flavour of the same one, so I am not going to quote low-calorie macros for it until I have its panel in front of me. If it comes back I will put the real numbers here.
Where to Get It
MyCore Supplements in Bishopstown, Cork bring it in from the United States, and as far as I can tell they are the only Irish stockist — it is not something you will find in a supermarket here.
Reader code NNF10 takes 10% off full-price items, it does not apply to anything already reduced, and no commission comes back to me on it. Full terms on the MyCore discount code page, or see all five reader codes.
Frequently Asked Questions
Is it worth the price over normal peanut butter?
If you are cutting, yes, and the reason is calorie density rather than protein content. If you are bulking or not tracking, ordinary peanut butter is cheaper and tastes better. This solves a specific problem: wanting the flavour when the calories are not there.
Does it taste like real peanut butter?
Close, not identical. Removing the fat changes the texture — it is thicker and less oily. The flavoured ones cover that better than Original does.
Will the sweeteners upset your stomach?
Erythritol and a large fibre load can do that to some people, and this has both. If sugar alcohols do not agree with you, start with less than a full serving.
Is the study on their website reliable?
It is six people over two weeks. The design is reasonable but the sample cannot carry the conclusion. Buy it for the label, not the trial.