If you've decided to try fasting, the next question is which kind. Skip whole days of eating? Stick to an 8‑hour window? Do the 5:2? Each one promises weight loss, and the internet has a loud opinion about all of them. A 2025 network meta‑analysis in The BMJ finally put them side by side: 99 randomized trials, 6,582 adults, every major fasting method measured against the others and against plain calorie counting. The results sort out which approach takes off the most weight, and they point to something more useful than a single winner. The method you keep doing is the one that pays off, and helping you keep going is the entire job Omadic's tools and nurses are built for.
The four ways people fast
Most fasting falls into one of a few patterns, and the review compared all of them against the standard alternative of just eating less every day:
- Alternate‑day fasting (ADF). You swap normal eating days with fasting or near‑fasting days, often capped around 500 calories. The most aggressive of the group.
- Whole‑day fasting, the family that includes the popular 5:2: eat normally five days a week, fast or eat very little on one or two.
- Time‑restricted eating (TRE), the gentlest version. You keep all your meals inside a daily window, like 16 hours off and 8 hours on (16:8). No counting, just timing.
- Daily calorie cutting is the odd one out here, since it involves no fasting at all, just eating a bit less around the clock. The review used it as the standard comparison every fasting method was measured against.
What the study found
Every approach beat eating without limits, which is the first thing worth saying out loud: structure wins over no structure. After that, a clear ranking emerged.
Alternate‑day fasting came out on top. Across the trials it took off about 3.4 kg more than unrestricted eating, the strongest result in the review and rated high‑certainty evidence. Whole‑day fasting, the 5:2 family, was next at roughly 2.4 kg. Daily calorie cutting landed at about 2.1 kg, and time‑restricted eating at about 1.7 kg. Put head to head in the shorter trials, alternate‑day fasting edged the others by a kilogram or so.
It did more than move the scale, too. Alternate‑day fasting drove the largest drop in BMI of any method. It also beat time‑restricted eating on triglycerides and total cholesterol, and the 5:2 on triglycerides and non‑HDL cholesterol. For long‑term blood sugar (HbA1c) and "good" HDL cholesterol, the methods came out about even. And in people with type 2 diabetes specifically, alternate‑day fasting produced an even larger drop, around 4.4 kg, though that's exactly the group that shouldn't try it without supervision, for reasons we'll get to.
Serious problems were rare. Across the trials that tracked side effects, almost everything reported was mild and familiar: hunger, constipation, nausea, a bit of dizziness, with a single severe case (a hypoglycemic episode and a fall). Fasting is well tolerated for most people. The hard part is keeping it up, and that turns out to be the whole story.
What happens over a year
This is where the study turns honest, and where it turns useful. Most of those trials were short. When the researchers looked only at the studies that ran 24 weeks or longer, the spread between methods narrowed and the lead alternate‑day fasting held in the short trials disappeared. Over the long run, intermittent fasting and plain calorie counting came out roughly the same.
The reason is the least surprising finding in the paper: people stop. Adherence held up well early on, and of the 74 trials that tracked it, most kept more than 80% of participants on plan. But in the year‑long studies it slipped, and only five trials ran a full year. The most demanding methods are the hardest to live with, which means the biggest early numbers tend to belong to the approaches people are most likely to quit.
That reframes the whole choice. A method that wins a 12‑week trial does nothing for you if you've abandoned it by spring. What actually predicts weight loss over a year is whether you can keep going, and the most aggressive plans are the ones people drop first.
So which one should you do?
For most people, time‑restricted eating is the place to start. It lost a little less weight than alternate‑day fasting in the trials, but it asks the least of you: no calorie math, no full fasting days, just a daily window you can hold for the long haul. That staying power is why Omadic starts you there, usually at 16:8, and tightens the window only once the current one feels easy.
Alternate‑day fasting and the 5:2 still have their place. If you want a faster start and can handle the intensity, the bigger early numbers are real. The catch is that "can handle the intensity" varies enormously from one person to the next, and pushing too hard is the quickest route to burning out, or, if you take medication, to getting into trouble. Matching the method to the person is a judgment call, and it's one of the first things an Omadic nurse helps you get right.
Why staying on plan is the whole ballgame
The study's real lesson is that consistency beats intensity. Every method here works while you keep it up, and the aggressive ones are simply the easiest to drop. That sounds obvious, and it's also the precise spot where people doing this alone come undone. They pick the most extreme plan they can find, go hard for three weeks, hit a rough stretch, and walk away.
Omadic is built around the opposite path. You begin with something you can actually sustain, your progress is tracked so you can watch it working, reminders keep the window and your meals on schedule, and a real person checks in when your momentum dips. The trials lost people slowly, month by month, and the year‑long ones lost the most. Sealing that leak is the entire point of the product.
It helps that progress is visible. A lot of the quitting in these studies happens in the quiet stretch after the first fast loss, when the scale stalls and motivation runs thin. Seeing the longer trend, getting a nudge on a hard day, and having someone in your corner who expects that plateau and coaches you through it is the difference between a method you tried and a method you kept.
Why this works better with a nurse
Fasting interacts with the rest of your health, and the more aggressive the method, the more that matters. The review's own data make the case: alternate‑day fasting delivered the biggest results in people with type 2 diabetes, and that's the same group for whom a full fasting day can send blood sugar dangerously low if their medication isn't adjusted around it. The biggest upside and the biggest risk sit in exactly the same place.
Every Omadic plan is overseen by licensed nurses and health professionals. They help you choose the method that fits your body, your schedule and your medications, start you at an intensity you can hold, and watch the things that count as you go: energy, blood sugar, how well you're recovering between fasts. If a fasting day is about to collide with a prescription, they catch it. If a plan is too much, they ease it back before you quit rather than after. They coordinate with your prescriber instead of working around them. Most fasting apps hand you a timer and wish you luck; the supervision this research keeps asking for is the thing we built into the product.
How Omadic puts it to work
- Guided time‑restricted eating to begin, with room to progress to the 5:2 or alternate‑day fasting if it suits you. The full menu the study compared, matched to you.
- Nutrition and macro tracking so your eating days support the result instead of undoing it.
- Medication and supplement reminders plus real‑time alerts on your watch that keep you consistent, which is the one thing the long‑term data rewards.
- Licensed‑nurse coaching through all of it, especially if you have diabetes, metabolic syndrome, or take medication that fasting can affect. (More on fasting and metabolic syndrome here.)
The BMJ review compared every popular way to fast and found they mostly come down to a single question: can you keep going? Answering that one in your favor is why Omadic exists.
Common questions
Which type of intermittent fasting is best for weight loss? In the 2025 BMJ review, alternate‑day fasting produced the most weight loss in the short term, followed by the 5:2, daily calorie cutting, and time‑restricted eating. But across trials of 24 weeks or longer the differences faded, so the best method is really the one you can sustain. Omadic starts most people on time‑restricted eating for that reason.
Is alternate‑day fasting better than 16:8? For short‑term weight loss, the review found alternate‑day fasting took off a bit more, roughly 1.7 kg more than time‑restricted eating in head‑to‑head trials. It's also harder to keep up, and that edge shrank in longer studies. Which one is right comes down to what you can realistically maintain.
Is fasting better than just counting calories? Not by much. The review found intermittent fasting and continuous calorie restriction produced similar weight loss and similar effects on cardiometabolic markers, especially over the long term. Fasting's real advantage is that for a lot of people, a clear eating window is easier to follow than counting every calorie.
Is intermittent fasting safe if I have diabetes? It can help, and the review found especially large weight loss in people with type 2 diabetes. It's also the situation where guidance matters most, because fasting can push blood sugar too low on certain medications. Omadic's licensed nurses tailor the plan to your medications and coordinate with your prescriber, never working around your medical team.
How long until I see results? Most of the trials were short, with a median follow‑up of about 12 weeks, and saw steady weight loss in that window. The longer studies showed the results hold as long as the habit holds, which is the part Omadic and your nurse are there to protect.
New to fasting? Start with how to break a fast the right way and why electrolytes matter on longer fasts.
Sources
- Semnani‑Azad Z, Khan TA, Chiavaroli L, et al. Intermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta‑analysis of randomised clinical trials. BMJ. 2025;389:e082007. Read the study (BMJ) · Full text (PubMed Central)
- de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine, 2019.