Alternate day fasting might be worth trying for weight loss

Everyone’s tried a diet at some point – counting calories, skipping dessert, cutting carbs. But here’s the catch: most of it doesn’t last. That’s where intermittent fasting comes in. Instead of limiting what you eat, it focuses on when you eat.

Now, scientists have tested whether it really works. A huge review published in The BMJ looked at 99 trials. Over 6,500 adults took part. Most had health issues. Most were women. Their average body mass index was 31, which falls under obesity.

This wasn’t a small review. It compared different types of fasting with standard calorie-cutting diets and unrestricted eating. And the results? Pretty interesting.

How these diets work

Let’s break down the main strategies. Time-restricted eating (TRE) means eating during a set time window each day, like 8 hours on, 16 off.

Alternate-day fasting (ADF) is exactly what it sounds like: you fast one day, eat the next. Whole-day fasting (WDF) usually follows a 5:2 plan – five days of regular eating, two days of fasting.

These were compared with daily calorie restriction and completely unrestricted diets (called ad-libitum).

Participants followed these plans for anywhere from three weeks to a year. Most trials lasted about three months. Some were high quality. Others, less so. But together, they gave us a clearer picture.

Alternate-day fasting works best

Among all the diets, alternate-day fasting came out on top. People following ADF lost around 3.4 kg more than those who ate freely. Compared to daily calorie restriction, ADF showed an extra 1.29 kg drop in weight. That’s not a huge difference, but it’s something.

ADF also did better than the other fasting types. It beat TRE by 1.69 kg and WDF by 1.05 kg. But here’s the twist: none of these differences reached 2 kg. That’s the threshold researchers say matters for people that are above weight.

Still, ADF had some extra perks. It helped lower triglycerides and “bad” cholesterol more than the other diets. Blood sugar? No changes there. Same for “good” cholesterol. But weight and lipids did shift a bit.

Result fades over time

For the first few months, all fasting plans helped people lose weight. But after six months, those differences faded. Only people eating without restrictions kept showing a clear gap.

Longer trials also showed another pattern: people dropped out. ADF had the highest dropout rate. In one year-long trial, only 22% stuck with it. The rest gave up.

Were there side effects? Yes. Mild ones. Hunger, constipation, maybe some dizziness. Nothing dangerous, but not exactly fun either.

Food quality matters

Here’s what the team from Colombia pointed out. A diet isn’t just a plan. It’s also the support, the structure, the advice, and what you eat on non-fasting days.

“The current evidence provides some indication that intermittent fasting diets have similar benefits to continuous energy restriction for weight loss and cardiometabolic risk factors. Longer-duration trials are needed to further substantiate these findings,” noted the study authors.

“Intermittent fasting does not aim to replace other dietary strategies but to integrate and complement them within a comprehensive, patient centered nutritional care model.”

In other words, it’s not about picking sides. Intermittent fasting isn’t better or worse by itself. It can work – if it fits the person.

The reality of alternate-day fasting

Intermittent fasting works. So does calorie restriction. ADF may give you a slight edge. But none of these are magic. And none of them guarantee long-term success without real change and support.

The numbers aren’t mind-blowing, but they tell us something. If you can stick with fasting, especially ADF, you may lose a little more weight and lower some risk markers. If you can’t, you’re not alone.

In the end, the most effective diet isn’t the trendiest or the one that shows the biggest weight drop in studies. It’s the one you can keep doing without burning out.

If you can follow a plan for a week, then a month, then maybe a year – without feeling miserable or deprived – then that’s a good sign.

The meals you eat should feel normal, not like a punishment. Your routine should fit around your life, not take it over. When your eating habits make sense, and you don’t dread sticking to them, that’s when real, lasting change has a chance to happen.

The study is published in the journal The BMJ.

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