Which Diet Is Best for Weight Loss? 8 Popular Diets Compared

New diets promising fast results appear all the time. Some have useful elements; others don't stand up to scrutiny. As a dietitian, here's my honest look at eight popular approaches, and what actually works.

Which diet is best for weight loss?

A large review of 121 trials with nearly 22,000 adults compared 14 popular named diets, including Atkins, Zone and Mediterranean. Most led to modest weight loss and better blood pressure over six months. By 12 months, the weight loss had largely faded for every diet.¹

Low-carb and low-fat diets also work about equally well. In a 12-month trial of 609 adults, a healthy low-fat diet and a healthy low-carb diet led to similar weight loss (5.3 kg vs 6.0 kg), with no meaningful difference between them.² In other words, the diet you can keep doing matters more than which one you choose.

1. Atkins (high fat and protein, low carb)

Atkins promises weight loss on a diet rich in protein and fat and very low in carbohydrates. The early phases are very strict and cut out almost all carbs, which can cause headaches, tiredness, constipation and irritability, and may lead to nutrient gaps.

In the review above, Atkins led to about 5.5 kg more weight loss than a usual diet at six months, but the effect faded by 12 months.¹ Low-carb diets also lowered LDL ("bad") cholesterol less than low-fat diets did.¹ High-fat, high-protein eating may not suit people with gout or kidney or liver disease.

Pros: quick early weight loss can be motivating, and it cuts out most processed carbs and alcohol.

2. Dukan (high protein, low carb)

Even stricter than Atkins, Dukan also severely restricts fat and replaces it with lean protein.

Pros: you'll likely lose weight, because the food rules make it hard to eat much.

Cons: it's extremely restrictive, with rigid rules and no flexibility, so boredom and dropping out are likely. It's very hard for vegetarians and vegans, nutrient gaps are likely, and weight regain is common.

3. 5:2 intermittent fasting

You eat normally five days a week and eat very little on two. A 2025 review of 99 trials found intermittent fasting led to similar weight loss and heart health changes as cutting kilojoules every day.³

Pros: some people find two hard days easier than cutting back every day.

Cons: it doesn't teach healthy eating habits, and fasting days make it hard to get enough nutrients. It isn't suitable in pregnancy or breastfeeding, for people with a history of disordered eating, or for people taking medicines for diabetes unless their doctor agrees.⁷

4. Paleo

Paleo is based on the idea that eating like our hunter-gatherer ancestors is better than a modern diet. Eating plenty of vegetables and fruit and avoiding highly processed foods is healthy, but the evolutionary argument doesn't hold up.⁶

Pros: it cuts out processed foods in favour of fresh whole foods.

Cons: it needlessly cuts out wholegrains, legumes and dairy, which can lead to nutrient gaps. It can be expensive and hard to keep up, and the emphasis on meat is a concern if that means lots of red and processed meat.⁶

5. Alkaline diet

The theory is that eating "alkaline" foods changes your body's pH to help you lose weight and prevent disease. It does encourage lots of fruit and vegetables. But food has little effect on your blood pH, because your body balances it naturally, and your stomach needs to be acidic to digest food.⁶ A systematic review found almost no research to support or disprove alkaline diets or alkaline water for cancer, and concluded that promoting them for cancer isn't justified.⁵

6. 1,200-calorie diets

To lose weight you need an energy deficit. Eating 1,200 calories (about 5,000 kJ) a day creates a large one, but what's safe depends on your body size, age, sex and activity level.

Pros: it's a clear way to make sure you're eating less, and weight loss can be quick.

Cons: strict tracking can become an obsession with numbers at the expense of nutrition. For many people 1,200 calories is too little, and it can cause hunger, tiredness, headaches and nutrient gaps. Muscle loss is likely without enough protein and strength training. A very low-energy diet is best done with professional support.

7. Blood type diet

Supporters say your blood type decides which foods are best for you. A systematic review screened more than 1,400 references and found no studies showing health benefits of blood type diets.⁴

Pros: it encourages fresh, unprocessed food and less takeaway and alcohol, which helps anyone.

Cons: it cuts out foods at random based on blood type, it's awkward if you share meals, and there's no scientific evidence behind it.⁶

8. No carbs after 5pm

There's no good evidence that avoiding carbs in the evening speeds up weight loss. If you cut out pasta, rice, potato or bread at dinner, you're simply eating fewer kilojoules. There's nothing "fat-burning" about the timing.

Do fad diets work?

Many fad diets lead to some weight loss at first, but their strict rules are hard to follow for long. That often leads to a cycle of weight loss and regain. Cutting out whole food groups can also cause nutrient gaps, tiredness and constipation, and may lead to an unhealthy relationship with food or disordered eating.⁶

Frequently asked questions

Which diet is best for weight loss?

No single diet is best. Most popular diets give similar, modest weight loss, so the best one is the one you can stick with long term.

Is low-carb better than low-fat for weight loss?

No. A 12-month trial found healthy low-carb and healthy low-fat diets led to similar weight loss.

Do fad diets work?

They may lead to some weight loss at first, but strict rules are hard to keep up and weight is often regained.

Does the blood type diet work?

There's no evidence it does. A systematic review found no studies showing health benefits of blood type diets.

Is it bad to eat carbs at night?

There's no good evidence that eating carbs in the evening causes weight gain. Total kilojoules across the day matter more than timing.

References

Research (PubMed)

1. Ge L, Sadeghirad B, Ball GDC, et al. Comparison of dietary macronutrient patterns of 14 popular named dietary programmes for weight and cardiovascular risk factor reduction in adults: systematic review and network meta-analysis of randomised trials. BMJ. 2020;369:m696. PubMed 32238384
2. Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion: the DIETFITS randomized clinical trial. JAMA. 2018;319(7):667–679. PubMed 29466592
3. 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. PubMed 40533200
4. Cusack L, De Buck E, Compernolle V, Vandekerckhove P. Blood type diets lack supporting evidence: a systematic review. Am J Clin Nutr. 2013;98(1):99–104. PubMed 23697707
5. Fenton TR, Huang T. Systematic review of the association between dietary acid load, alkaline water and cancer. BMJ Open. 2016;6(6):e010438. PubMed 27297008

Australian guidelines

6. Dietitians Australia. Fad diets. View source
7. Dietitians Australia. Intermittent fasting. View source

This article is general information and isn't a substitute for personalised advice. Speak to your practitioner about your situation.