Best protein bars for weight loss NZ: calories per 20 g

It is 3pm, you have not eaten since breakfast, and you want something that will hold you until dinner without wrecking the day. Two bars in front of you both say "20 g protein" on the wrapper. One costs you 170 calories and the other costs you 240. That gap is the whole article.

The short answer

• Rank bars by calories per 20 g of protein, not by protein alone. Quest Bar Birthday Cake is the lightest in our range at 170 calories for 20 g of protein.
• Smart Bar Salted Caramel is 177 calories with 18 g of fibre, and Smart Bar Mango Cream is 178. Grenade is 214 and MusclePharm Combat Sport is 240 for the same 20 g.
• The gap between the lightest and heaviest bar is 70 calories, or about 490 a week if you eat one daily. Real, but small.
• No bar burns fat. A bar only helps if it replaces something bigger you would have eaten anyway.

Why calories per 20 g of protein is the right number

Protein grams on the front of a wrapper tell you nothing on their own. A bar can hit 20 g of protein and still carry 11 g of fat and 20 g of carbohydrate around it, which is what MusclePharm Combat Sport does in 57 g and 240 calories.

Fixing the protein at 20 g and comparing what the calories do lets you compare bars honestly. It is the same logic behind ranking whey by protein per 100 calories, applied to something you eat with one hand.

Our sibling post ranks these bars by protein per dollar, a different question with a different winner. If money is the constraint, read that one.

Low sugar and low calorie are not the same thing

Grenade has 1.4 g of sugar per bar, and it is also the second heaviest here at 214 calories. Quest has 1 g of sugar and lands between 170 and 200 depending on flavour. Both are "low sugar", and only one is genuinely light.

Sugar is only one input. Bars replace it with sugar alcohols, soluble fibre and fat, and fat carries more than twice the energy per gram that sugar does. A wrapper claiming "1 g sugar" is telling you about one line of the panel and nothing about the total.

Sugar alcohols like maltitol and erythritol are worth knowing about too. They carry fewer calories than sugar and the label maths reflects that, but in the 10 g to 20 g range some people get bloating and wind from them. If one brand consistently upsets you, that is usually why.

Fibre is the part most people ignore

Quest Choc Brownie carries 17 g of fibre in a 60 g bar. Smart Bar carries 18 g. Grenade carries 6.7 g and Combat Sport carries 5 g. That is a big spread for products sitting on the same shelf.

Fibre is why the high fibre bars sit heavier in the stomach than their calorie count suggests. If you are eating a bar to get from lunch to dinner, that matters more than the flavour does. It also means jumping from no fibre bars to two a day is hard on your gut. Build up slowly.

The bars, ranked by calories per 20 g of protein

Every figure below comes from our own product data as at 2 September 2026. A single bar is one serving, so price per serve and price per bar are the same number.

The Legendary Foods Protein Donut is technically the lightest thing we stock at 160 calories for 20 g of protein, but every donut flavour is out of stock, so it is not ranked. Legendary singles are out of stock too, which is why the pastry and the sweet roll are priced from their multipacks.

Combat Sport is the cheapest bar in the range at $5.08 and the most expensive in calories. That is not a mistake on their part. It is built as a training snack, not a cutting snack.

What the research actually supports

Protein does two useful things while you are eating less. It keeps you fuller than the same calories of carbohydrate or fat, and it protects lean mass while the weight comes off.

The second one has decent evidence behind it. Morton and colleagues, in a 2018 review in the British Journal of Sports Medicine (bjsm.bmj.com/content/52/6/376), pooled 49 trials and found protein supplementation improved gains in lean mass and strength alongside resistance training, with the benefit flattening out around 1.6 g per kg of bodyweight per day. The ISSN position stand on protein and exercise lands in a similar range and notes that higher intakes help preserve lean mass in a calorie deficit.

What none of that says is that a bar causes fat loss. Energy balance does that. The bar is a delivery method for protein you were going to eat anyway, in a wrapper that survives a gym bag.

Where a bar fits in a real day

Say you are 75 kg, aiming at 1,800 calories and around 120 g of protein while you lean out.

Breakfast at 400 calories with 30 g of protein. Lunch at 550 with 40 g. A Quest Birthday Cake bar at 3pm for 170 calories and 20 g. Dinner at 650 with 35 g. That comes to 1,770 calories and 125 g of protein, with the bar taking under 10 percent of the day.

Swap that bar for Combat Sport and the day becomes 1,840 calories. Still fine, but you have spent 70 calories for the same 20 g of protein and a lot less fibre. Over a 12 week cut, eaten daily, that is close to 6,000 calories.

The mistake we see most often is treating a bar as free food. Two bars is 340 to 480 calories, which is a meal with less food volume than actual food. If you are reaching for two, eat one and make a shake instead. Powder is cheaper per gram, and our comparison of bars against shakes has the numbers.

Second mistake: buying the lightest bar you do not enjoy. A 170 calorie bar you leave in the drawer does nothing. A 214 calorie bar you eat instead of a pie is a win.

Where NZ Supps fits

We are based in New Zealand and dispatch same day on orders placed before 1pm, with free shipping over $99. Every bar in the table is stocked as a single, so you can try a flavour before committing to a box.

If you are cutting, start in the protein bar range and pick something under 190 calories. If most of your protein should come from powder instead, the whey range is cheaper per gram, and best protein powder for weight loss covers how to choose one. Not sure how the pieces fit together? Use find your stack and we will match products to the goal, not to the biggest basket.

What is the lowest calorie protein bar in NZ?

Of the bars we stock as singles, Quest Bar Birthday Cake is the lightest at 170 calories for 20 g of protein. Smart Bar Salted Caramel is next at 177 calories, and it carries 18 g of fibre against Quest's 12 g.

Are protein bars good for weight loss?

They help if they replace something bigger. A bar has no fat burning effect of its own, so one eaten on top of your normal meals slows weight loss rather than speeding it up.

How many calories should a protein bar have?

Around 200 is a sensible ceiling for a snack bar carrying 20 g of protein. Above 220 you are close to meal territory and should plan for it that way.

Is Grenade good for weight loss?

It is fine, just not the lightest option. Grenade is 214 calories with 1.4 g of sugar and 20 g of protein, so it is genuinely low sugar but mid range on calories. If you like it enough to eat it consistently, that is worth more than the 44 calorie gap to Quest.

What is the healthiest protein bar?

There is no single answer, though bars with 15 g or more of fibre and under 5 g of sugar fill you up best per calorie. Quest and Smart Bar both sit in that group.

How much protein do I actually need per day?

Roughly 1.6 g per kg of bodyweight is where the benefit levels off in the research, so a 75 kg person is looking at about 120 g. Our guide to protein per day breaks it down by bodyweight and training load. Sources: Morton et al. 2018, British Journal of Sports Medicine (https://bjsm.bmj.com/content/52/6/376); ISSN position stand on protein and exercise, Journal of the International Society of Sports Nutrition (https://jissn.biomedcentral.com/articles/10.1186/s12970-017-0177-8); Examine.com protein and satiety topic pages; NZ Supps product data as at 2 September 2026.