Low Carb vs Low Fat Diets: The Research-Driven Guide
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For years, the standard diet advice was that fat was bad.

People started shunning all fat sources and counting calories, buying low-calorie, high-carbohydrate, non-fat packaged foods and thought the pounds would melt off.

But then, something funny happened: the average BMI, obesity rates and most deadly health conditions of the first world began to rise.

Today, our mainstream health organizations still warn about the dangers of too much fat and calories. However, we as a population are dealing with all sorts of diet-related problems — including struggling to keep off the weight.

It turns out that the best advice for weight loss is actually opposite of what we’ve been told.

HIGH Fat, LOW Carb diets are best for weight loss and for long-term health.

We’re about to show you why this is the case by comparing the scientific results of low-carb diets versus low-fat/calorie-restricted diets, both for weight loss and for long-term effects.

Let’s dive in.

The Weight Loss Effects of Low Fat vs. Low Carb Diets

23 randomized, controlled studies reported in peer-reviewed journals were done to analyze the weight loss results of low fat versus low-carb diets. The timeline of the studies ranged anywhere from 12 weeks to two years.

Most of the studies showed significantly more weight loss in the low-carb groups, often 2-3 times more than the low-fat groups:

  • One study on subjects from the Philadelphia Veterans Affairs Medical Center over six months showed that those on a low-carb diet lost over three times more weight than those on a high-carb diet.
  • Another study performed at the University of Connecticut showed three times as much abdominal fat loss in men in the low-carb group versus those in the low-fat group, despite the low-carb participants eating more calories.
  • A third study conducted over a two year period compared a low-carb diet, a calorie-restricted Mediterranean diet, and a calorie-restricted low-fat diet. This study showed that the low-carb group lost more weight than the other two diets and also had improvements in triglycerides and HDL cholesterol.

Additionally, many of these studies revealed that those on the low-carb diets lost more of the unhealthy, visceral fat found around the stomach compared to those following the low-fat diets.

In most of these studies, the low-carb participants were able to eat as much as they wanted (also know as “ad-libitum”). There were a few times that calories were restricted in the low-carb groups, but even then, they lost slightly more weight than the low-fat groups.

This makes sense because low-carb diets tend to be more satisfying due to higher amounts of protein and fat. (Many low-fat diets of today also discourage eating too much protein.)

In most of the studies, those on the low-fat diets were also restricting their calories. Contrary to popular belief, this can actually cause long-term negative results for reasons we’ll go into shortly.

So how did our participants fare over the long term for weight loss on these diets?

The Long-Term Results of Low Fat/Low Calorie Diets

The key to a successful way of eating is being able to stick with it long-term. This was the conclusion made by researchers at the University of Toronto in 2014 after examining 59 scientific articles on weight loss, including 48 randomized control trials on the topic.

The short-term versus long-term results of contestants on The Biggest Loser are a perfect demonstration of this, including why restricting calories and fat grams is an ineffective weight loss method.

The diet these people were eating was broken down like this:

Low carb vs low fat diet

This is a low-fat, high-carb diet. It’s also big on calorie and portion control combined with intense exercise.

Though the results for many contestants were huge and even shocking, all but one person studied gained at least some (if not all) of the weight back, and some even put on more weight than when they started the show[*].

But that’s not all…

A researcher who followed the contestants six years after the show ended, found the long-term effects to be serious.

Though we’re mostly talking weight loss here, there are other long-term effects of these diets that you definitely want to avoid:

  • Cholesterol: Low-carb diets were shown to improve HDL (heart-healthy) cholesterol significantly more than low-fat diets. In some cases, HDL actually went down on the low-fat diets. While low-fat diets did lower total and LDL cholesterol in study subjects, the stats show the results didn’t last after 6-12 months.
  • Advanced lipid markers were also shown to improve in the low-carb group.
  • Blood sugar: There was only one study involving those with Type 2 diabetes where compliance was consistent, but 90% of those in the low-carb group either reduced or went completely off their medications for diabetes.
  • Triglycerides: Both diets led to lowered triglycerides, but more so in the low-carb groups.

These results give us a good look at low-fat versus low-carb results over a short timespan, as the majority of the studies analyzed lasted around a few months and much less than a year.

But what about the long-term aspects of these diets? What we must consider about low-fat diets is that they’re usually based around the idea of calorie restriction. The reasoning is that low-fat foods are less calorie dense and therefore lead to more weight loss.

But is this true over the long-term? Let’s look at the details.

The Harm of Long-Term Calorie Deficits

The reason fat is seen as the enemy of weight loss in low-fat groups is because fat has more calories per gram than protein and carbohydrates.

The problem is that long-term calorie restriction can be damaging. The biggest risk of a long-term calorie deficit is the change to metabolism.

Danny Cahill, one of the Biggest Loser winners who lost 239 pounds in seven months, is now burning 800 fewer calories per day than he was before! His body is not burning enough calories to maintain even his thinner physique. And this is six years later!

When you eat at a caloric deficit, your body downregulates your metabolism so that you expend fewer calories throughout your day. This can cause a weight loss plateau.

You then have to constantly fight cravings, hunger, and binges because low-calorie dieting greatly decreases leptin and ghrelin, hormones that regulate hunger and satiety. 

Lower levels of (or lack of) these hormones will make us feel ravenous and battle cravings all the time.

There’s this belief in the diet world that the faster we lose the weight, the better the diet is for weight loss.

But this is a myth and, as you can see from above, is actually harmful.

Instead, make choices that focus on overall health, allowing excess weight to come off gradually, healthfully and for the long term.

How The Low Carb Ketogenic Diet Helps You Burn Fat and Lose Weight

Eating a low fat diet promotes eating at a calorie deficit, which is not an effective tool for long-term weight loss.

So what is an effective tool for long-term weight loss?

Eating a low-carb, ketogenic diet.

The ketogenic diet focuses on eating plenty of healthy and satisfying fats and proteins that improve your health, keep the extra weight off and take away the worry of calorie counting, cravings or metabolic damage.

Ditch the Low Fat, Calorie Restricted Diet and Start to See Results

Traditional dieting advice is outdated and ineffective. In fact, low-fat, calorie restricted diets will sabotage your weight loss by damaging your metabolism and only lead to more cravings and weight loss plateaus.

A low-carb keto diet is the best tool for staying satisfied and avoiding problems associated with these other forms of dieting, and protecting our health.

Dr. Anthony Gustin is a board-certified sports chiropractor, functional medicine practitioner, entrepreneur, podcast host, and founder of Perfect Keto.

After growing his sports rehab and functional medicine clinics to six locations in San Francisco, he shifted his mission to help as many people as possible achieve optimal health and well-being.

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Responses (1)

  1. Great article but I am confused about something and would respectfully disagree on one point.

    Why does a low-fat / high-carb diet have to be low in calories?

    I know lots of people who eat far more calories than I do and they are on high-carb vegan diets. The eat tons of good, clean, whole foods and they are super healthy.

    Let’s take the internet-famous “Freelee the Banana Girl” for example.

    She eats about 5000 calories a day, mostly comprised of fruit, starchy carbs, and veggies.

    She is very thin, high-energy, curvy, and quite the gorgeous young lady.

    As a matter of fact, her diet and lifestyle got her completely off of thyroid meds and she’s far leaner and healthier than she’s ever been.

    I know lots of people who get tons of calories on a low-fat/high-carb diet and they are really fit.

    Keto works for me and lots of others that I know but maybe there is no one size fits all diet for everyone.

    So maybe the key to health is getting enough good, clean calories and not mixing fats and carbs together?

    It seems that mixing fats and carbs together is what produces the fat gains, A1C, high trigylcerides, and high bad cholesterol?

    The really obese people in America seem to be the ones who combine fats and carbs in large amounts at every meal. Isn’t this what the standard American diet really is?

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