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A Review of Popular Diets – What Are They and How Do They Work?

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Every year there seems to be a new dietary strategy flooding the fitness and weight loss world.

While some of these new dieting techniques can be beneficial, providing a new viable option or alternative for people wanting to lose weight, sadly, this isn’t always the case. In this article, we will review a series of different dieting techniques and strategies, highlighting how they work, if they are beneficial and the pros and cons for both.


Diet #1: The Atkins & Low-Carb / Ketogenic Diets

One of the most famous dieting strategies around and one which has survived several decades. Since the Atkins diet, many other forms of a low-carb diet have emerged, including a ketogenic diet which is now a mainstream diet within the fitness industry [1][2].

The Atkins diet is based on a 4 phase plan, here’s an overview.

Phase 1: High Protein and Fat with virtually zero carbs; much like the ketogenic diet it limits carbs to 20 grams per day.

Phase 2: Similar to above; however you will slowly add in some low-carb fruits, nuts and lower carb vegetables.

Phase 3: Towards the end of your diet when you reach your desired goal or weight, you will start to add in more carbs and fine-tune your diet.

Phase 4: This is the maintenance phase which incorporates more carbohydrates allowing dieters to find a sweet spot for their carb intake.

In the initial 2 phases the Atkins diet is very similar to normal very low-carb or ketogenic diets, which eliminates all forms of carbs and focuses on a high amount of fat and protein from sources such as meat, fish, dairy, oils, nuts, seeds, avocado etc.


  • Numerous studies have shown a very low-carb diet to be effective tool for weight loss, at least in the short term [3][4][5][6].
  • Other studies have shown it to be an effective method for improving important variables of health such as cholesterol, blood glucose, insulin, blood TAG and blood pressure readings/levels [7][8][9].
  • Forces a simple reduction in calories and generally improves the nutritional content of a diet by restricting an entire food group and most processed foods/sugars.
  • Can cause large amounts of weight loss at first due to changes in glycogen and water content, which motivate beginners to continue.
  • Allows for a large fat and protein consumption, which may suit some individuals who do not like or eat carbohydrates.
  • Some low-carb studies show improved satiety / reduced hunger, but again, this always comes down to personal preference and the individual [10][11].


  • May not be a long-term or maintainable way of eating, especially if an individual enjoys or needs carbohydrates.
  • Unlikely to be optimal for athletes or bodybuilders who require some carbohydrates to optimize performance and other aspects of muscle growth / recovery [12][13][14].
  • May be too restrictive for a lot of individuals, especially those that do not enjoy high fat / protein foods [15].
  • May be harder to stick with when attending social events, eating out, on vacation etc.
  • Large amounts of the weight may be re-gained when an individual re-introduces more carbohydrates.
  • Some individuals may experience side effects from low-carb diets, including fatigue and weaknesses [16][17].

Why It Works: It forces the restriction of an entire food group, which also restricts most processed foods. This limits an individual’s food choices and tends to limit them to lower calorie, whole foods, therefore, making it easy to produce a calorie deficit. It also has a high protein content, which can be beneficial for weight loss, satiety and lean mass retention [18][19][20].

Summary: Out of all the dietary trends, the Atkins diet and other low-carb diets do have some supportive research, especially for those with metabolic diseases such as type 2 diabetes or obesity. The main issue is conformity – while some people love a low-carb approach, many people have a hard time sticking with it in the long term.


Diet #2: Intermittent Fasting

Intermittent Fasting is another popular dieting technique with plenty of research supporting its use [21][22].

It’s based on the concept of long fasting windows with small eating windows. There are several different fasting approaches, with the most common being 8/16, 4/20 (feed/fast) or entire day on / day off fasts.

There are no specific dietary, food or macro nutrient restrictions within the feeding window. In fact, because it’s such as small window of food/calorie consumption, it actually allows more dietary freedom/flexibility. The fasting window normally continues after an overnight fast, or, in some cases is started in the early evening until the next morning.

Here are a few examples:

  1. Feed: 1pm – 9pm (8 hours), Fast: 9pm – 1pm (16 hours).
  2. Feed: 8am – 4pm (8 hours), Fast: 4pm – 8am (16 hours).
  3. Feed: 5 – 9pm (4 hours), Fast: 9pm – 5pm (20 hours).
  4. Day 1: Eat like normal, Day 2: Total fast or 500 calorie intake.


  • Another simple strategy to lose weight as it limits food intake to a small window of time per day, which most of the time results in a calorie restriction.
  • Plenty of research showing it to be highly effective for fat loss, especially in disease and obese populations [23][24][25].
  • Has also been shown to improve markers of health, including blood glucose, insulin, cholesterol and other important aspects of health [26][27][28].
  • Allows for more dietary freedom/flexibility in a specific window of the day, for example in the evening when dining with family or out socializing.
  • May suit individuals who are extremely busy in the day and stress about eating, which normally means they cheat on their diet or grab fast food.


  • May not be optimal for athletes or those wishing to add muscle, because of the large amounts of time without food/nutrients may impair performance, recovery, muscle growth and possibly stimulate muscle protein breakdown. However, this debate is still on-going and more research is needed to confirm this [29][30][31][32].
  • Large fasting window can increase hunger and may cause binge eating or large ‘cheat’ meals at night.
  • Large time without food may cause dizziness, fatigue and headaches, at least during the initial adaptation period. It may also not be suitable for type 1 diabetics, those with blood glucose issues or during pregnancy.
  • May not suit training time/window (i.e. in the middle of the day), where you would ideally provide food around the workout to maximize performance, stimulate MPS and recovery.
  • May not be a long-term lifestyle fix – some people love it, others do not.

Why it Works: As mentioned, it basically forces people into a calorie restriction as long as they are sensible within the small feeding window. It also allows more flexibility of food choice / consumption in the feeding window. Some people prefer 1 – 2 large meals per day when dieting, rather than 3-6 smaller meals or snacks.

Summary: As always, it can be a great and very successful diet for people trying to lose weight, especially those who are obese with a large amount of fat to burn. It’s probably not optimal for a bodybuilder or muscle growth. Nonetheless, it can, however, still work. Like with the low-carb diets, some people love IF whereas others hate it.


Diet #3: The Paleo / Caveman Diet

The paleo diet is another very popular and successful dieting technique. It has one simple rule, you can only eat “like a caveman” or like we would have eaten in Paleolithic times [33][34].

This limits an individual’s intake to single ingredient foods, including meats, fish, vegetables, nuts, oils, fruits etc.

There are no set macronutrient ratios or other specific principles. However, due to the food groups and limitations, it tends to be fairly high protein, moderate to high fat and low to moderate carbs.


  • Fairly easy and straightforward to follow once you learn the main foods/food groups.
  • Restricts most calorie dense and processed foods which are both easy to over-eat on and generally unhealthy, whilst not creating the same satiety levels.
  • Based on whole, nutrient dense single ingredient foods.
  • Still allows for a variety of all 3 macronutrients.
  • Impressive research and health benefits for weight loss, cardiovascular disease risk factors and metabolic diseases [35][36][37].
  • Because of the food groups, it likely forces a calorie reduction and an increase in protein, low-calorie foods and fiber, which is the perfect combination for weight loss [38][39].
  • Increases healthy fat and micronutrient intake, especially from foods such fish (omega 3), vegetables and fruits.


  • Although it teaches some great eating habits, there’s not necessarily a need to eliminate other non-paleo foods forever. As always, you can achieve a healthy balance basing most of your diet on these foods with smaller amounts of ‘processed’ foods for a treat/special occasion.
  • Because of the forced restriction, it again could lead to binge eating, large cheat meals and a bad association with food over some time. While some people commit to the paleo lifestyle long term, many try to use it as a quick weight loss tool and as always, can’t sustain it in the long term, rebounding and ending up in a worse position than when they started.
  • May eliminate some foods that provide added benefit, or, for specific people such as ‘hard gainers’ or athletes make it hard to consume adequate amounts of calories/carbs.
  • May force a 100% ‘clean eating’ mindset and diverts people away from the bigger picture, losing the appreciation for the most important basics such as a healthy balance, sustainability and the importance of calories/macros.

Why it Works: Like the other diets, it quickly cleans up the diet, reduces processed and calorie dense food while likely increasing protein intake, fiber intake and nutrient dense whole foods.

Summary: Another good diet built on lots of positive and healthy principles. Basing a diet on the Paleolithic principles is a great place to start; however, there isn’t a need to be 100% paleo forever and you can still build a healthy, sustainable balance between healthy foods and those that you love. Additionally, although the paleo foods and principles can lead to weight loss, you must still pay attention to calories and macros overtime, especially if you begin to plateau.


Diet #4: Flexible Dieting / IIFYM

Most Biolayne members will be well aware of the principles behind Flexible Dieting (FD) or If It Fits Your Macros (IIFYM). In short, it allows for a more flexible food intake as long as you meet your daily calorie/macro requirements.

Although this diet may not have the same degree of direct scientific research as the diets above, more supportive research is starting to emerge. Additionally, it abides to the basic laws of calories/macros, which have numerous research studies demonstrating their importance.


  • Allows individuals to remain flexible and versatile on their diet, which means they can match the social challenges of modern day life, enjoy their diet more and not totally restrict themselves.
  • This flexibility often allows for greater long-term success and less yo-yo dieting or weight re-bounding [40][41].
  • Most advocates will still emphasize the need to focus on whole, nutrient dense foods for the majority of the time, meaning they still achieve a healthy and nutritious diet.
  • It teaches the individual to count macros, learn the nutrient values of food and emphasizes the often overlooked fundamentals which is total calorie and macro intake.
  • By mastering the basics, many individuals can still get extremely lean on this diet, without eliminating the foods they love, or, social events for weeks and months.


  • As always with nutrition and fitness, the biggest issue is when people take the diet out of context and try to pack as much junk / processed food into their diet as possible.
  • This can lead to nutrient deficiencies and hunger, as these foods have a much higher calorie density, lower fiber quantity and do not signal our hunger hormones (leptin and ghrelin) in the same fashion.
  • For some people, with a more ‘all or nothing’ attitude or poor self-control, it’s easier to totally eliminate sweets or processed foods for a set period than try to just eat smaller amounts. As always, it depends on the individual and their preferences.
  • It may be too complicated for beginners or those that have no clue what a calorie or macro is. Although this can be fairly easy to learn, some people just want to follow a set plan or strict rules, for example, eat this, don’t eat that.

Why it Works: It makes people focus on the fundamental principles of nutrition, weight loss or muscle growth – calories and macros. If performed correctly and sensibly, it also allows for flexibility and a balance between whole foods and the odd bit of ‘processed’ food on occasions or as part of a daily balance. Over the long term, this can form an enjoyable and sustainable plan, without rapid weight re-gain, cheat meals or yo-yo dieting.

Summary: For a lot of people who take a sensible approach, FD or IIFYM can be a very successful and long-term dietary pattern. In theory, it is basically following a healthy diet with great dietary principles, but just allowing for moderated and controlled treats or balance. It also teaches the importance of calories or macros, which are now often forgotten about or overlooked since the rise of other diets, which wrongly preach that calories or macros do not count etc.


What’s The Best Diet?

As always, it depends. Hopefully you can now see that all the diets have both positives and negatives. By selecting the positive aspects from several diets, you can quickly build a very healthy and successful diet. As long as you enjoy this and can stick with it in the long term, this is likely the ‘best’ diet for you, your goals, preferences and lifestyle.

Ultimately, there is never one best diet for everyone, with 100s of different variables affecting this one question to rule them all. In summary, picking a healthy diet that you enjoy, see results from and can maintain for years to come is probably the closest we will ever get to the ‘best’ diet.



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About Rudy Mawer
Rudy Mawer

Rudy Mawer is human performance researcher and a certified Sports Nutritionist from the International Society of Sports Nutrition (ISSN). He has a first class bachelor's degree in Exercise, Nutrition and Health and a Master's degree in Exercise and Nutrition Science. Rudy has worked as a sports nutritionist and trainer for 7 years, and has helped...[Continue]

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