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By R.Davies, PhD・Bodyweight
Published June 24, 2026 | 5 min read
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The weight loss diet industry is worth billions of dollars, so there’s a new “revolutionary” diet every few months. It arrives, it’s promoted, it’s adopted, it fails, it’s forgotten, then repeat. Does anyone remember the grapefruit, cabbage soup or tapeworm diet?
Most of them are forgotten within a year, even the ones that partially work or may have a bit of scientific evidence behind them. Paleo diets, keto diets and the carnivore diets all fall under this category.
The diets that actually work (and keep working) tend to stand the test of time. They’re tried and tested, and they tend to share the same few quiet, unglamorous features. In this article, we’ll name three of the best ones. We’ll discuss what drives fat loss from a dietary standpoint, identify what works and then (in our opinion) give you the three best dietary approaches that are proven and sustainable.
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Before comparing diets, it is worth being clear on the basics. Fat loss happens when your body uses more energy than you consume — a calorie deficit. This is not controversial; it’s physics and facts. You can’t really lose a significant amount of fat without a calorie deficit.
Where diets differ is how they help you reach, and then maintain, the calorie deficit. Some diets work by increasing how full you feel. Some diets rely on temporary motivation, mind games, willpower or strict rules. Some make overeating more difficult. Some are even able to shift your hormone balance. However, the “best” (or most effective) fat loss diets are the ones that make it easy to eat slightly less food, so they can be sustained long-term. Here are a few common features of them.
Most of the debate around fat loss over the last few decades has been low-carb versus low-fat. But, until recently, the third macronutrient, protein, had tended to be overlooked. Eating dietary protein preserves muscle while you’re losing fat, it makes you feel fuller for longer, and it contains fewer calories, gram-for-gram, than fat and carbohydrate (when you account for its thermic effect).
Several studies have shown that high-protein diets produce better fat loss outcomes compared to lower-protein equivalents [1].
High-fibre foods slow digestion, stabilise your blood sugar levels, and reduce your appetite. They also tend to have lower energy density, which means you can eat a larger volume of food for fewer calories. Diets rich in vegetables, legumes, and whole grains are consistently associated with better weight outcomes [2]
Adherence is probably the most underrated factor of all. And the research is unusually consistent here: across well-designed head-to-head diet trials, the differences in weight loss between dietary approaches largely disappear when adherence is the same.
We see this all the time, where a new diet may outperform another (more established) one over 3 or 6 months. But by 12 or 24 months, fat loss is roughly the same. In other words, the best diet is one you can stick to forever, or at least long enough to reach a healthy bodyweight (after which it can be adjusted). A year is usually the minimum. So, before you commit to any diet, think about whether you can see yourself following it in a year.
The Mediterranean diet is not designed as a fat-loss diet, but it consistently outperforms a lot of “weight loss” diets. Over 2 years, people who followed a Mediterranean diet lost more weight (and maintained it better) than people who followed a standard low-fat diet and had better adherence than those who followed a low-carbohydrate diet.
The diet works for fat loss partly because of how it is structured. Olive oil, nuts, legumes, and fish are all filling and have their own health benefits. The high fibre content from vegetables, fruits, and whole grains slows digestion and blunts your appetite.
It is also a diet that is flexible, varied and enjoyable, which matters more than you think for long-term adherence. It has historical roots, so it comes with a story, plenty of recipes, textbooks, research and other lots of other resources. This makes it accessible and easier to start and follow than most other diets.
A lot of the popular fat-loss fad diets tend to sacrifice health for quick results. Whereas the Mediterranean diet is the opposite. It has probably the largest body of evidence supporting its health benefits. Even without any weight loss, the diet is shown to support cardiovascular health, metabolic health, brain and mental health, life expectancy, and quality of life. It is really unparalleled.
A high-protein diet is typically defined as one where protein makes up over 25% or more of total calorie intake (or over 1.2 grams per kg per day) — meaningfully above the average of 15–17% in most Western diets. Technically, high-protein diets don’t focus on any particular food group, though they, de facto, tend to lean towards eating more lean meats, fish, eggs, dairy, and legumes than normal.
The case for higher protein for fat loss is the strongest of any of the macronutrient changes. Protein is the most filling macronutrient — it reduces the release of your “hunger hormones” and increases “satiety signals” more than carbohydrates or fats do. It also has the highest “thermic effect”, meaning around 20–30% of the calories in protein are used to digest it. And lastly (and most importantly), it preserves muscle mass while in a calorie deficit, which makes fat loss a lot easier.
Studies show that high-protein diets produce better fat loss outcomes than lower-protein diets, even when total calories are the same [4][5]. However, there are some practical challenges. Some very high protein intakes can become repetitive and expensive. So, we recommend moderate increases (e.g., at least 20% calories or 1 gram per kg a day), which should be layered onto another healthy dietary pattern (e.g., the Mediterranean diet). Just reaching a high daily protein target isn’t enough by itself, especially if you also want to maintain (or improve) your health while losing fat.
Intermittent fasting is not a “diet” in the traditional sense — it is about when you eat rather than what you eat. The most common formats are time-restricted eating (typically a 16-hour fast with an 8-hour eating window, known as 16:8), alternate-day fasting, and the 5:2 approach (normal eating five days a week, very low calories on two non-consecutive days).
Intermittent fasting produces comparable results to standard “continuous” calorie-restriction diets when total calorie intake is the same [7]. These short intermittent fasts do not offer any special metabolic advantages, but they do offer a structure that many people like and can follow.
Compressing your eating into a shorter window naturally reduces the opportunity to eat, without having to count and keep track of your calories and/or macros all day long.
Most intermittent fasting protocols report meaningful fat loss (and health benefits). However, in our opinion, the 16:8 has the best returns. It is the highest ranking results, adherence, and it fits around normal sleep and daytime eating patterns.
In practice, what it means is eating your breakfast later, your dinner earlier, or rolling either of them into your lunch or a daytime snack. Out of the two of them, the early window seems to be marginally better, where you stop eating earlier in the day (commonly referred to as “early time-restricted eating”).
Intermittent fasting is flexible and not a complete dietary approach, so it can be combined with other eating patterns (e.g., Mediterranean or high-protein diet). But like other diets, the key to successfully implementing it is finding a fasting protocol that you can maintain, that fits your schedule and lifestyle.
The best fat-loss diet is not the one that promises the fastest results in the shortest time. In fact, that is probably a red flag. The diets that tend to work best create a moderate (ideally, barely noticeable) calorie deficit. Good fat-loss diets don’t rely on willpower, preserve your muscle mass, are healthy, nutritious, and fit your life well enough so you can follow them for months and years, not days or weeks.
Mediterranean-style diet, higher than average protein targets, and time-restricted eating each do this in their own way — and all three are flexible enough to adapt to your personal preferences and routine. If you want to do your own thing, the easiest gains can come from simply eating a bit more protein and fibre, and reducing ultra-processed food intake.
1. Leidy HJ et al. The role of protein in weight loss and maintenance. Am J Clin Nutr. 2015 Jun;101(6):1320S-1329S. PMID: 2592651
2. Koliaki C. Defining the Optimal Dietary Approach for Safe, Effective and Sustainable Weight Loss in Overweight and Obese Adults. Healthcare (Basel). 2018 Jun 28;6(3):73. PMID: 29958395
3. Shai I et al. Dietary Intervention Randomized Controlled Trial (DIRECT) Group. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Engl J Med. 2008 Jul 17;359(3):229-41. PMID: 1863542
4. Clifton PM et al. Long term weight maintenance after advice to consume low carbohydrate, higher protein diets — a systematic review and meta-analysis. Nutr Metab Cardiovasc Dis. 2014;24(3):224–235. PMID: 2447263
5. van Baak MA, Mariman ECM. Dietary Strategies for Weight Loss Maintenance. Nutrients. 2019 Aug 15;11(8):1916. PMID: 3144323
6. Enríquez Guerrero A et al. Effectiveness of an intermittent fasting diet versus continuous energy restriction on anthropometric measurements, body composition and lipid profile in overweight and obese adults: a meta-analysis. Eur J Clin Nutr. 2021 Jul;75(7):1024-1039. PMID: 33293678
Published: June 24, 2026
Lead Author: R.Davies, PhD, MRes, BSc, CPT, FHEA | Author Bio
Dr Davies is a physiologist specialising in human health, performance and nutrition.
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