← Blog

Zero Drinks & Your Training: Do Diet Sodas Help or Hurt Fat Loss?

Cola Zero, Rivella Zero, sugar-free energy drinks: an honest, non-alarmist look at zero-calorie drinks for people who train — sweeteners, fat loss, cravings and a simple rule for the shop.

---

Cola Zero, Rivella Zero, Pepsi Max, sugar-free ice tea, Red Bull Zero — the "zero" shelf keeps growing, and if you're training and watching your weight, it's an obvious pull: the taste of a soft drink with none of the sugar or calories. But is that a free lunch, or a catch dressed up as a health choice?

This is an honest, non-alarmist look at zero-calorie drinks for people who train. We're not here to sell you a scare story about sweeteners, and we're not here to pretend a can of Cola Zero is health food. We'll separate what the evidence actually says from the myths on both sides, and give you a simple rule for the shop.

The short version: For most people who train, zero drinks are a useful tool, not a health drink. As a swap for sugary soft drinks they genuinely help fat loss. As an extra habit on top of water, they add little and can nudge cravings and dental wear. Water stays the base; a zero drink is the better second choice, not the first.

What "zero" actually means

A "zero" or "diet" drink replaces the sugar with non-nutritive sweeteners — usually aspartame, sucralose, acesulfame-K, or steviol glycosides (stevia), often in a blend. The result is a drink that tastes sweet but carries roughly zero calories and zero sugar.

That much is real and worth being clear about: a can of Cola Zero has essentially no calories, where a regular cola has around 35–40 g of sugar and 140–150 kcal. Over a day of two or three drinks, that's a meaningful difference — the kind that quietly decides whether someone is in a calorie deficit or not.

Do zero drinks "break" fat loss? The myths

The internet is full of confident claims that diet drinks secretly wreck fat loss. Here's what holds up and what doesn't.

• "They spike insulin and make you fat." For the common sweeteners, the honest answer is: not in any way that matters for body fat. Sweeteners don't provide calories, and any small physiological blips don't add up to fat gain on their own. Fat loss is still decided by your overall calorie balance.
• "They break a fast." If your fast is about calories, a zero drink (plain, no milk) is essentially calorie-free and won't break it in that sense. If your fast is a strict medical or religious one, that's a different definition — judge it by your own rules.
• "Diet soda makes you eat more." This is the one with a kernel of truth, but it's individual. For some people a sweet taste with no calories does nudge appetite or cravings later; for many others it does the opposite and helps them stay on plan. The studies are genuinely mixed. The practical takeaway isn't "avoid" — it's notice how you personally respond.

The clean summary: a zero drink won't secretly cause fat gain. What it can do is influence your appetite and habits, and that effect runs in both directions depending on the person.

The honest case for zero drinks

For a lot of people who train, zero drinks earn their place:

• As a sugar swap, they're a real win. Trading two regular colas a day for the zero version removes ~70–80 g of sugar and ~300 kcal without any willpower cost. That's often the single easiest calorie cut on a diet.
• They make a deficit more livable. A sweet, fizzy drink for almost no calories can be the thing that keeps someone on a lower-calorie phase instead of quitting it. Adherence is what makes a cut work — see our guide to eating for muscle growth and when to cut.
• They beat "rewarding yourself" with sugar. A zero drink after a hard session is a far cheaper reward than a sugary one.
• Some are a caffeine hit without the sugar. A sugar-free energy drink or a Cola Zero delivers caffeine for training without the sugar load (more on that below).

None of this makes them healthy in the way water or tea is. It makes them a useful downgrade from sugar — and on a diet, that's valuable.

The catches worth knowing

Just as honestly, zero drinks aren't free of downsides:

• Cravings and the sweet-taste habit. Keeping everything intensely sweet — even calorie-free — can keep the taste for sweetness dialled up. For some people that makes it harder to be satisfied by plain food. If you notice that, dialling sweetness down over time helps.
• Dental wear. Most colas and many zero drinks are acidic, and the acid erodes enamel regardless of sugar. Sipping them all day is worse than drinking one with a meal. This is a genuine, underrated downside.
• Gut comfort. Some sweeteners and sugar alcohols can cause bloating or looseness in sensitive people, especially in quantity. If your stomach objects, that's your answer.
• They're not hydration heroes. They hydrate you, but so does water — without the acid, caffeine or the habit loop. For daily fluid, water and unsweetened tea are simply better.
• The habit stacks up. Four or five a day is a lot of acid, caffeine and artificial sweetness running through your day, even at zero calories. "Zero calories" doesn't mean "unlimited."

Are the sweeteners safe?

This is where the internet gets loudest, so let's be straight and measured.

The common sweeteners — aspartame, sucralose, acesulfame-K, stevia — are among the most-studied food ingredients there are, and food-safety authorities (including in the EU/Switzerland) consider them safe within the acceptable daily intakes, which are set well above what normal drinking reaches. In 2023 the WHO's cancer agency classified aspartame as "possibly carcinogenic" (group 2B) — the same broad category as pickled vegetables and aloe vera — while the WHO's own intake committee kept the acceptable daily intake unchanged, noting you'd need to drink many cans a day, every day, to approach it.

The honest read: for normal consumption — a couple of drinks a day — the sweeteners are not something a healthy adult needs to fear. Separately, the WHO has advised that non-sugar sweeteners shouldn't be relied on as a long-term tool for weight control — which fits the theme of this article exactly: use them to swap out sugar, not as a health drink you build a diet around.

If you're pregnant, have a specific medical condition (e.g. PKU, which is flagged on aspartame products), or simply prefer to avoid them, that's a completely reasonable choice — reach for water, sparkling water, or unsweetened tea.

Energy "zero" drinks specifically

Sugar-free energy drinks (Red Bull Sugarfree, Monster Zero, and the like) are really two things in one: a zero-sugar soft drink and a caffeine dose. As a pre-workout, the caffeine is the useful part — roughly 80 mg in a 250 ml can, similar to a strong espresso; larger cans stack higher.

Treat them as a caffeine source, not a soft drink you sip all day:

• Time it, don't graze it. Caffeine ~30–60 minutes before training is where it helps performance.
• Watch your daily total. Coffee, tea, cola and pre-workout all add up; most healthy adults do fine up to ~400 mg a day, but late-day caffeine wrecks sleep — and sleep drives your recovery.
• Zero sugar still isn't zero effect. The caffeine, acid and sweetness are all still there. "Sugar-free" only removes the sugar.

A quick look at the Swiss shelf

You'll find the whole zero range in Migros, Coop, Denner and the discounters. The pattern is consistent, so you can judge by category rather than memorising labels:

Two label traps worth knowing: "no added sugar" isn't "zero sugar" (a fruit-based drink still carries its own sugar), and "light" or "less sugar" isn't "zero" either. If the number matters to you, read the per-100 ml figure, not the front of the can.

A simple rule for zero drinks

You don't need to overthink it:

1. Water and unsweetened tea are your base — most of your fluid, most days.
2. Use a zero drink to replace a sugary one, not to add on top. That's where it actually helps.
3. Keep it to a couple a day, not a constant sip-all-day habit — for your teeth, your caffeine total and your sweet tooth.
4. Notice your own response. If a zero drink leaves you craving more sweet things, that's useful information; if it keeps you on plan, keep using it.
5. Around training, judge energy drinks by their caffeine, and time it — don't treat them as hydration.

The bottom line

Zero drinks aren't the villain some make them out to be, and they aren't a health drink either. For someone who trains and is managing their weight, they're a genuinely useful swap for sugar: they cut real calories, make a deficit easier to stick to, and — in normal amounts — the sweeteners aren't something to fear. The catches are real but manageable: acid on your teeth, a possible nudge to your sweet tooth, and the temptation to treat "zero calories" as "unlimited."

Keep water as the base, use zero drinks to trade down from sugar rather than adding on top, and you get the upside without much of the downside.

Use zero drinks to replace sugary ones, not to add to your day. As a swap they help; as an all-day habit on top of water, they mostly add acid, caffeine and sweetness for little gain.

Drinks are a small piece of the puzzle — what really moves the needle is your overall training and nutrition working together. With GetMyCoach you get a plan that thinks training and nutrition as one: built around your goal, your everyday life and your progress.

Build my plan for my goal →

Last updated: July 2026. This article is general nutrition and training information, not medical advice. Sweetener safety assessments and acceptable daily intakes are set by food-safety authorities and can be reviewed over time; product recipes, caffeine content and availability vary by brand and can change, so check the current label when it matters. If you're pregnant, have a medical condition, or are sensitive to caffeine or sweeteners, seek advice tailored to you.