Which Diet is the Best for Fat Loss? There May Be More Than One

Brad Dieter
Written By: Brad Dieter
April 25th, 2016
Updated: June 13th, 2020
Categories: Articles Nutrition
34.5K Reads
Which Diet is the Best for Fat Loss? There May Be More Than One
So many diets claim to be the best for fat loss. Take a look at the science behind popular fat loss diets and figure out which diet may work best for you.

Many bar fights have started and relationships ended while arguing over whose diet is best.

I mean put a clean eating person and an IIFYM person in the same room and only one will leave alive.

Ok, that’s probably a hyperbole. It really isn’t that bad, but there is such polarizing dogma present in the nutrition world.

It can be hard to make sense of the myriad of diet schemes and try to uncover the truth.

About a decade ago, I decided I wanted to find some answers and figure out what the truth is about diets and weight loss.

I wanted the real truth, the scientific truth, not just the popularized version of the truth. This required a solid 10 years of learning the ins and outs of each diet.

Aside from research studies and articles, personal experience is also a key piece of understanding diets.

To this notion, I have personally tried each of the major diet approaches (sans vegan, sorry vegans I tried it for like 3 days and just couldn’t handle it). So, I have intimate knowledge of how they actually work in the real world.

This article is a culmination of about 10 years of reading, learning, and asking questions.

I am going to give you my honest reflections and thoughts of a 10 year journey and elucidate on the key principles of diets and weight loss.

I’ll get this out of the way now; there will be some anecdotes put forth in here. Yes, I know those are poor substitutes for rigorously controlled studies, but they should cause you to pause, think, and reflect on the realistic application which they may provide.

Related: The Ultimate Guide to Meal Prep with Recipes

Diet Paradigms and Their Successes

To start the journey, I think it is only appropriate to begin by looking at some of the most popular diets, their basic principles, and whether they have been successful


The Paleolithic Diet, aka the Paleo Diet, is based upon the idea that our current food environment is at odds with our evolutionary heritage and that the optimal diet is to mimic that of our Paleolithic ancestors.

Best Fat Loss Diet Paleo

The basic tenets of this diet are to 1) avoid: processed foods, grains, legumes, and dairy, 2) consume: lean meats, fruits, vegetables, and “healthy fat”.  Also, calorie counting is not generally promoted by the Paleo Diet; food quality is the primary focus.

In general, it adopts a more low-carbohydrate stance. It tries to minimize starch intake. Often times the types of foods people consume on a Paleo diet shifts their macronutrient intake to a high protein, high fat, and low carb diet.

Human Research

A recent study demonstrated that a 10 day excursion on a paleo diet was capable of improving insulin sensitivity and favorably altered blood triglycerides1. Another study showed that a Paleo diet lead to improvements in glycemic control and cardiovascular risk factors in patients with T2DM. Importantly, they also showed that the Paleo Diet led to “spontaneous caloric restriction”2.


Read the Full Paleo Transformation Here


If it fits your macros (IIFYM)/ Flexible Dieting is based solely on the concept of calories in vs calories out. Weight loss and body composition are simply a math equation.  You use a calculator to determine your energy needs and then just eat foods to fill those exact numbers.

The type of foods you eat doesn’t matter in the equation. 100 grams of carbohydrates from a sweet potato and from pixie sticks are equivalent. Essentially, a calorie is a calorie and it doesn’t matter where it comes from.

Human Research

Unfortunately, I was unable to find any well conducted trials on “calorie based weight loss” irrespective of food quality to present. However, there are some interesting case studies to suggest the notion of a calorie is a calorie holds at least some weight in this debate.

Personally, I find the “Professor loses 27 pounds by eating only Twinkies” self-experiment rather interesting and shows us that weight loss on “junk food” is actually possible. Ideal, No. Possible, Yes.



The Zone Diet focuses on boosting the body’s anti-inflammatory responses through eating anti-inflammatory food sources. These food sources are generally veggies and fruits. Another important component of the Zone Diet is restricting grains and starches.

The diet focuses on portion control. A general meal would include a third of it coming from some lean protein source and the other 2/3rds coming from colorful veggies and/or fruit low in sugar. Finally, an additional monounsaturated fat source (olive oil or almonds) is added to meal.

The diet highlights meal frequency, encouraging its dieters to consume 3 full meals a day and 2 snacks to promote satiety.

Human Research

One study in T2DM, overweight women, a Zone Diet was more effective for weight loss and reducing triglycerides than a high-carbohydrate diet3. Another trial comparing Zone, Atkins, Weight Watchers and an Ornish diet also showed that a Zone diet was able to reduce body weight and markers of heart disease4.

Importantly, so did the other diets, and they found that dietary adherence was the biggest factor in weight loss, not the exact type of diet.



The Ketogenic diet is based on a physiological mechanism by which restricting carbohydrates causes your body to run primarily on fat and induces the process of nutritional ketosis. During ketosis your liver produces ketones for your brain and other select tissues to run on instead of glucose.

Consuming a high amount of dietary fat and a low amount of dietary carbohydrates are the key features of a ketogenic diet. Exactly how high fat and low carb? Traditionally, strict ketogenic diets are structured with about 70-75% of your daily caloric intake coming from fat and about 5% from carbohydrates.

The range of carbohydrates you can consume and stay in ketosis varies from person to person but you can usually eat up to about 12% of your daily caloric intake and stay in nutritional ketosis.

Best Diet Ketogenic

Practically, consuming protein about .8 grams per pound is enough to kick you out of ketosis.

So ideally, to optimize a ketogenic state and maintain lean mass your diet should be about 75% fat, 5% carbohydrates, and 20% protein.

Human Research

In one study, a short term (4 week), high-protein, low-carbohydrate ketogenic diet reduced hunger, led to spontaneously lower food intake, and induced roughly 12 pounds of weight loss in seventeen obese men who were studied in a residential trial5. Another study demonstrated that a ketogenic diet was more effective than a low-fat diet at for weight loss (9.9 lbs in ketogenic vs. 4.4 pounds in low-fat)6.


Read the Full Ketogenic Diet Transformation


The Mediterranean diet is based upon the epidemiological findings that those who live in Greece, Italy, and Spain and consume traditional diets of their culture have better health measures than the rest of the world. The key features of this diet is high consumption of olive oil, legumes, fish, vegetables, whole cereal grains, and moderate consumption of cheese and yogurt.

Human Trials

In a large clinical trial published in the New England Journal of Medicine showed that a Mediterranean diet was successful in helping participants lose weight (about 9 pounds), had high adherence (~85% after 2 years), and improved glucose sensitivity7.



Clean eating is a relatively simple concept. It focuses solely on food quality and essentially is about eating whole foods that are unprocessed or minimally processed. The goal is to eat foods that are in their natural form.

Human Trials

As “Clean Eating” is not really a traditional “diet”, there are not any well conducted studies to draw from so I have to rely on anecdote alone.


Read the Full Clean Eating Transformation


Lets stop and take a quick recap.

  • Each of these seemingly disparate diet philosophies was able to induce weight loss and improve health markers in either research studies, clinical trials, or case studies.
  • In virtually all cases weight loss was commensurate with calorie reduction, either spontaneous or forced.
  • While calorie intake appears to be a major driving in weight loss in these studies, it appears that the quality of food, and maybe the type of macronutrients you consume can influence the degree of weight loss and impact health parameters.

Part II: A Deeper Examination of Diet Principles

What I hope was clear from Part I is that each of these diets are quite different from each other. Yet, they all appear to be able to induce fat loss and improve health. How is that possible? Lets dive into it.

On the surface, these diets often fall into two camps: 1) it’s all about calories (i.e. IIFYM, Weight Watchers), or 2) its all about food quality (i.e. Clean Eating, Paleo).

Related: 10 Best Muscle Building Meals at Big Chain Restaurants

The issue is often polarized, with people adopting a stance at either end of the spectrum. Well, as with most things the real truth is in the middle: Calories play a huge role in your weight, but the composition of your food also dictates it.


The idea of caloric balance is not a new one; it has been around for millennia. The ancient Greeks had a very good understanding that eating too much resulted in weight gain and advised moderate food consumption.

The foundation of the argument for caloric balance being the driving causative factor in weight gain or weight loss is thermodynamics.

Put simply, the first law of thermodynamics is that energy cannot be created or destroyed, simply converted. The reasoning then follows, if we consume more energy than we expend we must store it in the form of fat (our bodies most stable way to store excess energy).

Best Fat Loss Diet IIFYM

This argument does indeed hold merit. When we really look through the literature it is abundantly clear that hypercaloric states can lead to weight gain while hypocaloric diets can lead to weight loss. It appears regardless of the macronutrient approach you take, altering the quantity and quality of your diet can result in weight loss8.

In fact, most successful dietary protocols, whether low-carb, high-protein, low-fat, have one underlying theme in successful studies. They tend to reduce overall caloric intake.

Many studies state that non-energy restricted “macronutrient shuffling” can result in weight loss. Although they are not restricting energy on the face, they often are reducing their overall caloric intake. Research refers to this as “spontaneous caloric restriction”. Simply put, people just naturally consumed less calories.

Calories do matter. They matter a whole lot. However, the story isn’t as simple as calories-in and calories-out, especially when it comes to weight-loss.

When you look at all the research, that is precisely what you find. Both the quantity and quality of what you eat play a role in both weight gain and health. It is an intricate dance of the two.

The Battle for Macros

Clearly calories matter. However, I believe the greatest point of contention in the nutrition sphere is the macronutrient ratio.

Best Fat Loss Diet Calories Matter

Let's ditch the dogma and instead use the scientific evidence to tease out the real answer. In order to do so, we need to look at how macronutrient ratios affect weight in the scientific literature.


Over the past 3 decades, low-fat diets have been nutritional dogma when it comes to weight-loss (except for the Atkin’s Diet which did its best to carve out a niche in the 90’s and 2000’s). It was simple, fat makes you fat and reducing fat was the way to lose weight. Does research show it to be effective?

You bet it does10,11,12. I understand that the studies sighted were energy-restricted, that is not the argument here. I am simply stating that low-fat diets can be effective for weight loss. 

It is likely that reducing fat intake is effective in weight loss based on the simple idea that fat is more calorically dense. Swapping out 9kcal (fat) for 4kcal (protein or carb) per gram of food is an easy way to reduce overall calorie intake.

Do studies suggest that low-fat diets are optimal for weight loss? No, they absolutely do not. Do they indicate they are optimal for improving health? Again, no they do not. What they do show is that low-fat diets can and do result in weight loss and can be one dietary tool used in a nutritional program.


Similar to low-fat diets, low-carb approaches can also result in weight loss13,14,15.

Related: 10 Unusual Carbohydrates You've Probably Never Eaten

Why might that be?

I think there are several explanations for this, beginning with the simple one. In these studies the subjects were only restricted in their carbohydrate or fat intake (depending on which arm of the trial they were in) and instructed to eat ad libitum in the other macronutrients.

Reducing overall carbohydrate intake was probably achieved by either choosing more leafy-greens and fibrous vegetables and/or increasing protein and fat consumption. Thus, resulting in greater satiety (due to increased protein/fat) and reduced the caloric density of their carbohydrates.

Best Diet for Fat Loss Low Carb

When all of that occurs together you have the ideal environment to reduce caloric intake. Less caloric density and greater satiety.


For years I was convinced that food quality was the single most important factor in obesity. I was wrong. Yes, I will admit I have changed my perspective (learning, growing, and changing your perspective is important in life).

In the context of weight-loss, food quality is important, but I think calories may be a bigger driver of weight loss*.  What spurred the change in my perspective?

Related: 43 Best High Protein Recipes That Anyone Can Cook

Well first, there are all the studies where it looks like different macro-nutrient ratios and dietary strategies are effective in weight loss. The single most common theme amongst them is a reduction in caloric intake.

Second, are some compelling stories of individuals who have lost weight eating only Subway, the professor who ate only Twinkies for 27 days, and the person who lost weight eating only McDonalds. Clearly, it is possible to lose weight eating “low-quality foods”.

Best Diet for Fat Loss Big Mac

Now don’t confuse losing weight with optimal health. The quality of your food effects a lot of physiological processes that can ultimately lead to disease states (i.e. CVD, hypertension, etc.).

Clearly we do not want to eschew food quality, as micronutrition and other aspects of food can impact your health. We simply use these examples to illustrate the point that you can lose weight eating only “low quality” foods.

Resolving the Paradigms

When we take all of the information presented above into consideration we get a picture that appears complicated but in reality is quite simple. There are countless dietary approaches and each one can be successful if calories, macronutrients, and food quality are accounted for. We can boil down most of diets and weight loss paradigms into the following key concepts.

1) Calories play a major role in weight gain and in weight loss. Our internal mechanisms for regulating food consumption and body fatness is not built for our current food environment.  We live in an environment with highly rewarding, energy-dense, nutrient-poor foods.

2) One of the biggest contributors to that environment is processed carbohydrates, specifically sugar and the ability to consume large amounts of it fairly unknowingly.

We cannot rule out fat as a large contributor to this environment either. Fat is the most energy dense macronutrient, provides a very appealing mouth feel, and when combined with sugar or salt promotes overconsumption.

This does not mean processed foods have to be avoided at all times. Just be aware that caloric control takes more care, thought, and planning when eating a diet high in processed carbohydrates and fat.

3) To avoid weight gain from overconsumption, it would be prudent to eat a diet well balanced in the macronutrients, consuming more carbohydrates if you are extremely active and less if you are sedentary.

Best Diet for Fat Loss Well Balanced Meal

4) Don’t fret about the perfect ratio, instead focus on nutrient-dense, non-industrialized foods. If you want carbohydrates, eat a sweet potato with a little butter. If you want some protein, eat some simply roasted or braised meat. If you want some fat, leave the skin on your chicken or have some veggies with olive or coconut oil.

There is a place in your diet for “dirty foods”, just ensure that they fit within your calorie and macro goals.

5) If you are overweight or obese, it is a little more nuanced, but still simple. Reducing your caloric intake can result in weight-loss.

6) Each dietary strategy has pros and cons and you can use whichever framework best fits your lifestyle and personality.

  1. Metabolic and physiologic improvements from consuming a paleolithic, hunter-gatherer type diet
  2. Beneficial effects of a Paleolithic diet on cardiovascular risk factors in type 2 diabetes: a randomized cross-over pilot study
  3. Comparison of high-fat and high-protein diets with a high-carbohydrate diet in insulin-resistant obese women
  4. Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease Risk Reduction
  5. Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum
  6. Effects of a low-carbohydrate diet on weight loss and cardiovascular risk factor in overweight adolescents
  7. Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet
  8. Effects of Low-Carbohydrate vs Low-Fat Diets on Weight Loss and Cardiovascular Risk FactorsA Meta-analysis of Randomized Controlled Trials
  9. Effect of an energy-restricted, high-protein, low-fat diet relative to a conventional high-carbohydrate, low-fat diet on weight loss, body composition, nutritional status, and markers of cardiovascular health in obese women
  10. Energy Restriction and Weight Loss on Very-Low-Fat Diets Reduce C-Reactive Protein Concentrations in Obese, Healthy Women
  11. The Effects of Low-Carbohydrate versus Conventional Weight Loss Diets in Severely Obese Adults: One-Year Follow-up of a Randomized Trial
  12. A Low-Carbohydrate as Compared with a Low-Fat Diet in Severe Obesity
  13. A Randomized Trial of a Low-Carbohydrate Diet for Obesity
  14. A Randomized Trial Comparing a Very Low Carbohydrate Diet and a Calorie-Restricted Low Fat Diet on Body Weight and Cardiovascular Risk Factors in Healthy Women