Best energy bars for ultra running and runners (UK)

Written by James Frost, founder of Flaming Phoenix. Updated October 2026. Flaming Phoenix makes Phoenix Bars, one of the five bars compared here.

The best energy bars for ultra running are the ones your stomach still accepts after ten hours on your feet, eaten in pieces to supply the 150 to 400 calories an hour that the International Society of Sports Nutrition suggests for ultras. Of the five bars compared here, my top pick is Phoenix Bars. They carry the most calories per bar by far, up to 557 in a compact, 120g bar, about twice the next biggest, so one bar broken into pieces covers more than two hours, two bars clear an 800-calorie kit reserve, and a bar mixed with water becomes porridge at an aid station or overnight.

Bars do a different job from gels in an ultra. Gels and drink cover the hard running, when chewing is awkward. Bars and real food cover the climbs, the night and the last third of the race, when your pace drops and sweet things start to turn your stomach. This page is about that second job.

Which bar for which part of an ultra?

• Best overall, and for long, slow ultras, night sections and multi-day races: Phoenix Bars, up to 557 calories in a compact, lightweight 120g bar (we make these).
• Mandatory kit food reserves: Phoenix Bars, where two bars clear an 800-calorie reserve.
• Fast running sections, alongside a gel or drink: Styrkr BAR50, 50.4g of carbohydrate in a 70g bar.
• Walked climbs: Mountain Fuel FeelGoodBar, 274 calories from oats, dates and flaxseed.
• A fruit-and-nut bar: Veloforte Di Bosco, 238 calories from dried fruit, almonds and pistachios.
• Nut-free: OTE Anytime, 240 calories from gluten-free oats.
• Everyday running and marathon training: see the runners section below.

How did we compare ultra bars?

I compared five bars sold by UK running brands on the four things that decide whether a bar actually gets eaten in the second half of an ultra: how kind it is to a tired gut, how well it works eaten slowly in pieces over many hours, how it fits an aid-station and drop-bag plan, and how many you need to meet a mandatory kit food reserve. Calories, carbohydrate, fat and fibre come from each brand's own product page, checked October 2026.

Flaming Phoenix makes Phoenix Bars. They are judged on the same four tests, and they come out on top on the two where the numbers are clearest: hours covered per bar, and the number of bars needed for a kit reserve.

What makes a good energy bar for ultra running?

A good ultra bar is easy on a tired gut, breaks into small pieces you can eat over an hour or two, and still tastes acceptable at 3am.

Gut tolerance. The ISSN position stand on ultra-marathon nutrition advises avoiding highly concentrated carbohydrate and dehydration to reduce stomach trouble, and practising your race food in training well before race day. Fat and fibre slow digestion, and that is more of a problem while you are running than on a walked climb. On the labels: Mountain Fuel has 15.4g of fat and 5.1g of fibre per bar, Veloforte 7.6g and 4.4g, and Styrkr BAR50 8.5g and 1.9g. If your stomach is the weak link, our guide to gut training for ultras sets out how to build tolerance over a training block.

Eating slowly for many hours. At ultra pace you are not eating one bar and moving on; you are nibbling for 10, 20 or 30 hours. Bars that break cleanly into chunks make that easier. Christian Poulton, on the Winter Spine Challenger South, wrote: "I ate the bars slowly by breaking them down into chunks and consumed a couple every 30 minutes." Sweetness is the other problem: after many hours plenty of runners start craving savoury food, and our guide to the best foods for ultra running sets out what works at each stage of a race.

Aid stations and drop bags. What you carry only has to fill the gap between aid stations, so check the race's spacing before you decide how many bars go in your vest. Put the bars you trust in your drop bags; whatever is on the aid-station table may not suit your stomach. A quick habit that helps: break a bar into pieces at the aid station, bag them, and keep the bag in a front pocket so you eat as you walk out. Our guide to drop bags and aid stations covers the rest.

Mandatory kit. Some UK races require an emergency food reserve on top of what you plan to eat, so it needs to be compact and to keep for months in the bottom of a vest. The rules differ a lot from race to race; the section below works through one real example.

How much should you eat per hour in an ultra?

Aim for 150 to 400 calories an hour in an ultra, made up of 30 to 50g of carbohydrate, 5 to 10g of protein and some fat. That is the range in the 2019 ISSN position stand, which also warns against long spells below 200 calories an hour in longer races. For your own race, the ultra running calorie calculator sets your estimated burn against an hour-by-hour plan.

Here is what each bar gives you at a steady 250 calories an hour, a middle-of-the-range target:

• Phoenix Bar (529 to 557 calories, up to 66g carbohydrate): one bar lasts about 2 hours 10 minutes and gives up to about 30g of carbohydrate an hour.
• Mountain Fuel FeelGoodBar (274 calories, 30.7g): one bar lasts about 65 minutes, about 28g of carbohydrate an hour.
• Styrkr BAR50 (249 calories, 50.4g): one bar an hour, about 51g of carbohydrate an hour.
• OTE Anytime (240 calories, 39.9g): just under an hour, about 42g of carbohydrate an hour.
• Veloforte Di Bosco (238 calories, 35.8g): just under an hour, about 38g of carbohydrate an hour.

One Phoenix Bar covers more than two hours of that range by itself, which is why it is the bar I would build an ultra around. On fast running sections, add a carbohydrate drink or a gel alongside it.

The best energy bars for ultra running, ranked

Per-bar figures from each brand's label, checked October 2026.

1. Phoenix Bars: best overall, and best for long, slow ultras, night sections and multi-day races.
Phoenix Bars carry up to 557 calories in a compact, lightweight 120g bar (441 to 464 per 100g), with up to 66g of carbohydrate and up to 19g of protein, about twice the calories of the next biggest bar here. They are soft, break cleanly into pieces and keep for up to two years, so the same bar works in a vest pocket, a drop bag and a kit reserve. One bar broken into pieces covers more than two hours at 250 calories an hour, two bars clear an 800-calorie kit reserve, and mixed with water a bar becomes porridge at an aid station or overnight. £5.25 a bar. Steven Southern took two on a six-hour trail marathon training run: "we were out for 6 hours I took only two of these with me, digest really well".

2. Styrkr BAR50: for fast running sections.
249 calories and 50.4g of carbohydrate in 70g, with 8.5g of fat, 1.9g of fibre and 2.5g of protein. A crisp rice bar, vegan and gluten-free. At 356 calories per 100g it suits a 50km or a supported 100km, eaten alongside gels and drink, more than a self-supported week.

3. Mountain Fuel FeelGoodBar (Date & Salted Caramel): for walked climbs.
274 calories in 60g (about 457 per 100g), with 30.7g of carbohydrate, 15.4g of fat and 5.1g of fibre, built on flaxseed, gluten-free oats and dates. The fat makes it filling on a long climb in the dark; it is the bar on this list I would least want to eat while running hard.

4. Veloforte Di Bosco: a fruit-and-nut bar.
238 calories in 55g, 35.8g of carbohydrate, 4.5g of protein and 4.4g of fibre, made from dried fruit (34%), almonds (19%) and pistachios. It tastes like food, not a sports product, and the fibre and nuts suit climbs more than hard running.

5. OTE Anytime (Lemon Drizzle): a nut-free option.
240 calories in 62g, 39.9g of carbohydrate and 7.5g of fat, from gluten-free oats, golden syrup, butter and honey. It is gluten-free and nut-free but contains butter, so it is not vegan. A soft oat flapjack that sits well before a run.

How many bars cover a mandatory kit food reserve?

It depends on the race: the 2026 Ultra X England kit list asks for an "Emergency food reserve (800kcal minimum)", while Centurion's Thames Path 100 rules ask for at least 1 litre of water capacity and list no emergency food. For an 800-calorie reserve:

• Phoenix Bars: 2 bars, 1,058 to 1,114 calories, 240g.
• Mountain Fuel FeelGoodBar: 3 bars, 822 calories, 180g.
• Veloforte Di Bosco: 4 bars, 952 calories, 220g.
• OTE Anytime: 4 bars, 960 calories, 248g.
• Styrkr BAR50: 4 bars, 996 calories, 280g.

Phoenix Bars clear the reserve with the fewest items and the biggest margin: two bars, more than 1,000 calories, and one less thing to dig for at kit check. Check your own race's rules each year, as kit lists change, and see our ultra marathon kit list for the rest of what goes in the vest.

What are the best energy bars for runners?

For everyday running and marathon training, the best energy bar depends on when you eat it. During a run, choose the highest-carbohydrate, lowest-fat bar you can chew at pace. Before a run, pick a soft oat bar you already know agrees with you. After a long run, have something with protein and plenty of calories that you will actually eat. From the five bars on this page:

• Long runs, long days on your feet and the hours after: Phoenix Bars, up to 557 calories, up to 66g of carbohydrate and up to 19g of protein in a compact, lightweight 120g bar, eaten in pieces as you go (we make these).
• Fast efforts and marathon pace, with a gel or drink: Styrkr BAR50, 50.4g of carbohydrate with 1.9g of fibre.
• An hour or two before a run: OTE Anytime, a soft oat flapjack with 39.9g of carbohydrate.
• Steady training runs, if you want food-first ingredients: Veloforte Di Bosco, made from dried fruit, almonds and pistachios.
• Trail and fell runs where you walk the climbs: Mountain Fuel FeelGoodBar, 274 calories from oats, dates and flaxseed.

For a marathon or a two-to-three-hour training run, how fast the carbohydrate goes in counts for more than total calories. Most sports nutrition guidance puts the target at 30 to 60g of carbohydrate an hour for efforts longer than about 90 minutes, which is half a Phoenix Bar an hour, one BAR50 an hour, or a smaller bar plus a gel. My guide to marathon fuelling sets out a full race-day plan, and the running calorie calculator works out what a given run burns. On shorter trail and fell races, the guide to trail running food covers when gels or real food work best, and if gels stop going down, see energy gel alternatives.

What is a good natural energy bar for running?

A good natural running bar is one whose ingredient list starts with foods you recognise, such as fruit, nuts or oats. Phoenix Bars are built on gluten-free oats, Veloforte leads with dried fruit and almonds, Mountain Fuel with flaxseed, oats and dates, and OTE with oats, golden syrup and butter. Taste is personal, and with six Phoenix Bar flavours you can mix a few on your long runs and find your favourite.

Multi-day and self-supported races

On a multi-stage race where you carry a week of food, calories per gram decide the pack. Phoenix Bars are the densest here, at up to 464 calories per 100g, against about 457 for Mountain Fuel and 356 for BAR50, and they carry about twice the calories per bar; our ranking of the highest calorie bars in the UK compares more brands per gram. Our high calorie bars can also be stirred into water as a breakfast porridge, which saves carrying a separate breakfast; see how to use Phoenix Bars. A backyard ultra turns the hourly rhythm into a loop, and backyard ultra nutrition sets out a lap-by-lap rotation. For the whole race-day plan, see our guide to ultra marathon running nutrition.

Frequently asked questions

How many bars do I need for a 50-mile ultra?
At 250 calories an hour, a 12-hour 50-miler needs about 3,000 calories. If you plan to take roughly half from aid stations, carry the other 1,500: three Phoenix Bars broken into pieces (1,587 to 1,671 calories), or about six standard bars of 240 to 275 calories, plus a few gels for the faster sections.

Can you run an ultra on bars alone?
On slow, mountainous or multi-day ultras, many runners eat mostly bars and real food, and a Phoenix Bar, with up to 557 calories, covers more than two hours on its own. On faster races it is hard to reach 30 to 50g of carbohydrate an hour from bars while running, because chewing at pace is difficult, so most people mix bars with drink and gels. Test the mix on long training runs first.

What is the best energy bar to eat before a run?
A soft, low-fibre bar eaten 60 to 90 minutes before you start, so it has time to settle. A third to half of a Phoenix Bar works well, or a whole bar mixed with water as a porridge breakfast a couple of hours before a long run; OTE Anytime is another soft oat option.

What are the best energy bars for long runs?
For runs over about 90 minutes, a bar you can eat in pieces as you go. A Phoenix Bar carries up to 66g of carbohydrate and up to 557 calories, so one bar broken into pieces covers a two-hour run at about 30g of carbohydrate an hour; on faster runs, add a gel or drink.

Which energy bars are easiest to digest while running?
Soft bars eaten in small pieces usually sit best, and runners describe Phoenix Bars as easy to digest: Steven Southern wrote that they "digest really well" on a six-hour run. Eat them in small pieces, little and often, alongside your usual drinks.

Do bars go hard on a winter ultra?
Some do. Date-based and chocolate bars firm up near freezing, which makes them hard to bite on a night section. Phoenix Bars won't freeze: Christian Poulton, on the Winter Spine Challenger South, found they stayed soft enough to eat at around freezing. Carry the next few hours of food in an inside pocket, broken into pieces, so it is to hand.

Sources: Tiller et al., International Society of Sports Nutrition position stand on single-stage ultra-marathon nutrition (2019); Ultra X England 2026 kit list; Centurion Thames Path 100 2026 rules; product pages for Styrkr BAR50, Veloforte Di Bosco, Mountain Fuel FeelGoodBar and OTE Anytime. All checked October 2026.