Why do Low Carb Diets Work? Here’s 6 Scientific Reasons!

Remember when the Atkins Diet was such a big deal in the 90s?

woman holding ham dish

Even though Atkins was widely regarded as a ‘fad’, there are still numerous people around the world who swear by it.

The creator of Atkins alleges you can lose up to 15 pounds in the first two weeks alone - a startling claim considering that on average you can’t lose more than one to two pounds per week safely on a diet.

Here’s the thing, though.

Even though the media may think Atkins was a fad, scientific studies show it really does work, as do similar low-carb diets.

Losing 15 pounds in two weeks isn’t typical, but it is possible.

And even if you don’t, odds are if you do a low-carb diet like Atkins properly, you will lose weight steadily and successfully.

In fact studies suggest low carb diets lose more weight and more fat mass than low fat diets (1)

But How Does It Work?

Since you’ve found your way to this page, it’s evident that you don’t want to just hear that you can lose weight using a low carb diet.

You want to know the science behind how it works.

That is a very smart attitude to take, because there are a lot of diets which are proven to help you lose weight, but not necessarily over the long term, and not necessarily in a healthy way.

You want to be sure that a low-carb diet is a safe, healthy approach before you dive in.

The truth is, there may not be just one mechanism that explains how low-carb diets work.

Scientists are still studying them, and they seem to offer a number of weight loss and overall health benefits (2).

These benefits all combine to help you achieve the weight loss success you are looking for.

Let’s take a look at them now.

Test your knowledge now or come back after reading this article to check your learning:​

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Low Dietary Carb Intake Reduces Insulin Levels

steak with rocket salad

First, let’s talk for a moment briefly about fat.

Fat is your body’s way of storing energy for long-term supply.

Your fat stores are a kind of emergency reserve fuel.

Your body does not store them for everyday use - you break into them when your food supplies are low (usually).

But you also break into them when you reduce your carbohydrate intake, even if you are otherwise eating plenty of food.

To explain why, we need to look at insulin (hormone) and blood sugar.

While insulin controls the serum nutrients circulating throughout our body, its principal action is on glucose (blood sugar).

Insulin has the job of telling your body to pull glucose out of your blood and burn it for energy.

The more carbohydrates you eat, the higher your blood glucose levels are going to be, and the more insulin is secreted to pull out this glucose.

Your blood glucose is your first source of energy to burn, before your fat.

That means when you are burning blood glucose for energy instead of fat, your fat stores remain untouched.

Your body always turns to those blood glucose stores first and falls back on your fat as a backup plan.

If you always provide your body with plenty of blood glucose in the form of dietary carbohydrates, you are simply never going to reach that point where you need to turn to your fat.

The backup plan remains simply that: a backup plan.

In this process, insulin inhibits fat burning (lipolysis) (3).

When you reduce your carbohydrate intake, two things happen:

  1. You stop raising your blood sugar. This means there is less glucose available to utilize as energy. This scarcity means your body must press on to plan B - your fat stores.
  2. Less insulin is secreted, dropping your insulin levels, which means you reduce the amount of the hormone that inhibits fat burning.

Here is a graph of a comparison study on low carb diets for insulin levels over a 24 hour period (40):

low carb insulin level graph

But wait, it doesn’t stop here.

Insulin also activates the production of fat (lipogenesis) of which a proportion will be stored (4)

So reducing insulin also reduces fat production and storage.

low carb flow chart

Multiple studies have demonstrated how low carb diets significantly reduce serum insulin levels (5, 6, 7, 8, 9).

KEY POINT: Reducing dietary carbohydrates directly reduces blood levels of insulin.

Low insulin levels allow fat burning and high levels encourage fat production.

Low Carb Diets Are Protein-Rich, and Protein Helps You Lose Weight

Most low-carb diets also tend to be high in protein.

This is something of a coincidence since there is nothing about carbohydrate intake which directly inhibits protein intake.

But when you eat less of one type of macronutrient (carbohydrate, protein, and fat), you have to replace it with another.

Most high-carb foods happen to be high in sugars and grains also happen to be low in protein.

It is common to replace carbohydrate-rich foods with protein-rich foods like eggs and meat. This boosts your overall protein intake.

low carb macronutrient ratio pie chart

As it turns out, in the majority of studies comparing the weight loss achieved from low carb vs low fat diets, the low carb diets have been protein rich.

Protein helps you lose weight through several mechanisms (10):

For one, satiety goes up and appetite goes down (11, 12).

Since you feel fuller and satisfied, you are less likely to overindulge. More on that shortly.

For another, your metabolism receives an overall boost, helping you burn more calories throughout the day (13, 14, 41)

Eating protein helps maintain muscle mass which supports our metabolism and calorie burning not only while we are working out, but also while we are resting.

Finally, if you work out with adequate protein intake, you can build muscle.

Increasing your muscle mass to fat ratio can increase your resting metabolism (15).

Keep in mind that this benefit is for those who incorporate resistance/strength training into their lives (16).

You cannot expect to build muscle mass without effort, simply by eating protein - you have to challenge your body physically .

If you do, you can look forward to burning more calories around the clock.

KEY POINT: Low carb diets tend to be high in protein. Protein has the benefit of increasing metabolism, increase satiety, reduce appetite and maintain muscle mass.

A Low Carb Diet Helps You Lose Water Weight

scale and measure tape

Coming back to that claim that you can burn 15 pounds in your first two weeks on phase 1 of the Atkins diet, how does that work?

Well, whether it works or not probably depends on how much water weight you have retained in your body.

If you have a good deal of water weight, you will probably notice a huge improvement in the first couple weeks, because a low-carb diet helps you shed that water weight rapidly.

If you don’t have much water weight, you will not notice such a huge change in the beginning, but that means you were just ahead of the curve to begin with.

There are two reasons that you lose water weight when you stop eating so many carbs.

When your insulin levels drop, your kidneys start excreting sodium (17).

This helps you shed your excess water weight, and also has the bonus of lowering your blood pressure (18).

The other reason is that glycogen binds water in your liver and muscles.

Carbohydrates are stored as glycogen (19).

Fewer carbohydrates in your body equate to less glycogen.

That means your body stops binding water in your muscles and liver and is free to release that water.

Even if you drop calories dramatically on a high-carb diet, this effect is not nearly as pronounced.

Don’t worry; you don’t need that water weight for anything. It literally is nothing more than excess weight.

A side benefit is that typically low carb dieters experience less bloating.

You may have heard people say, “The low-carb diet does not actually work; it only drops your water weight, not your fat.”

This is a misperception.

Low-carb does reduce your water weight, but it also helps you burn fat for reasons you are now starting to understand.

Read on to find out more.

KEY POINT: The rapid weight loss experienced in the first 2 weeks of low carb is explained by reduced insulin and glycogen which in turn causes the body to shed water.

By Itself, Low Carb May Speed up Your Metabolism

One study (20) conducted on participants across a 4-week period on a series of different diets (low fat, low glycemic index, and low carbohydrate) found that a low-carb diet boosted energy expenditure at a rate of approximately 250 calories per day in comparison to other types of diets.

KEY POINT: If you have tried to lose weight by exercising, you know that burning an extra 250 carbs a day is quite a challenge, and can take up to an hour of moderate intensity exercise.

Low carb can burn those calories without the exercise.

Low Carb Makes You Feel Full and Satisfied, so You Are Less Likely to Overeat

woman holding sauage with fork

There are a lot of reasons why people overeat, but one of them is feeling hungry even though you have had plenty of food.

Some types of food are more satiating than others.

Protein is one such food (20, 21) and may have a direct effect on weight loss (22, 23).

Many people overeat because they are not getting enough protein in their diets.

Even though they are eating plenty of calories, they still feel a need to eat more.

This forces them to take in additional calories which they have no hope of burning.

The result? They put on weight.

If you have ever tried a low-fat diet, you have probably noticed the focus is on calorie restriction.

But you have to get energy from somewhere.

That is why a low-fat diet can become uncomfortable and even dangerous past a certain level.

With low-carb, you do not focus on restricting calories, and you get plenty of energy.

You get full at an appropriate time because you are eating protein-rich foods.

These foods help you feel satiated when you have eaten the right amount of calories.

Ketosis also has an impact (24). When you are on a ketogenic diet, you may only feel hungry for 1-2 meals per day.

Research also shows that low carb diets may regulate ghrelin and leptin (25, 26). These two hormones regulate your appetite.

This not only makes a low-carb diet a healthy, natural alternative to a low-fat diet but also helps you break bad habits and gauge correctly when you are really full.

It also makes a low-carb diet easier to stick with than a low-fat diet.

In fact, many research studies which compare low-carb and low fat dieters take this into account.

The low-carb dieters can eat until they are full, while the low fat dieters have their calories restricted (27).

Guess who loses more weightUsually it is the low-carb groups.

KEY POINT: Low-carb is safer and healthier than low-fat, and easier to maintain over the long-term since you are getting plenty of energy and feeling full after meals.

Say Goodbye to Unhealthy Processed Foods and Sugars

Man showing hand gesture saying

Highly processed foods are bad for your health, as are sugars.

Foods that are high in sugars and artificial additives tend to be high in carbohydrates.

In fact, sugar is a carbohydrate.

That means when you start decreasing the carbohydrates in your diet, you automatically stop eating sugar-rich foods and heavily processed foods.

Research shows that eating heavily processed foods has adverse nutritional results (28).

Heavily processed foods are also addicting and can prompt overeating (29).

Sugar is also highly addictive (30). It may even be more addictive than cocaine (30).

Sugar is high in calories and therefore leads to weight gain. It may also lead to cardiovascular disease and other serious health conditions (31).

Throwing junk food out is a great decision since it will not only help you to lose weight but will also improve your digestion and metabolism and overall well-being.

Also consider the fact that you are going to be replacing those junk foods with healthy, wholesome foods that are rich in nutrition.

So instead of stuffing yourself with empty carbs, you will be providing your body with what it needs to function at its very best.

When you trade in French fries for carrots and celery, you not only lose weight but feel great.

KEY POINT: By lowering dietary carbohydrates, you naturally reduce heavily processed foods and sugars.

Heavily processed foods and sugars are addictive, and they correlate with health conditions such as heart disease and diabetes.

Benefits, Drawbacks, and Cautions for Following a Low Carb Diet

Cheerful medical personnel showing hand gesture

Reading through this list, you have now learned how a low carb diet can help you lose weight, and you've had a chance to peruse just a few of the many scientific research studies backing up its efficacy.

You have learned some of the additional health benefits of a low carb diet as well.

Here's more:

  • Build muscle mass for a sculpted physique by eating more protein (32, 33, 34, 35). Remember, you can only enjoy this benefit if you work out.
  • Improve metabolism (36).
  • Improve digestion. When you quit eating unhealthy processed foods and sugars, you give your system a break (37).
  • Reduce blood pressure, LDL cholesterol and triglyceride levels for a healthy, balanced cardiovascular system (38).
  • Boost your levels of HDL cholesterol (38)
  • Reduce your risk of heart disease by improving cholesterol levels.
  • Burn fat in your liver and belly (39). These visceral fat stores are particularly unhealthy. Eliminating them can help reduce inflammation and prevent disease.

Any drawbacks you should be aware of?

Before you jump in, you should be aware that dropping your carbohydrate intake quickly can result in temporary side effects like constipation, fatigue, dizziness, headache and mental fog.

You can prevent these problems by drinking plenty of water and ensuring you are getting all the nutrition you need to function.

Remember, these side-effects are temporary. Once your body adjusts to burning fat, they will pass (40) .

This diet is not for everyone, though it is safe for most people.

If you take insulin or diuretics, suffer from kidney disease, are pregnant, or are breastfeeding, consult with a doctor first.

One more cautionary note is this:

A low-carb diet will only remain effective over the long term if you stick with it over the long term.

A lot of people begin a diet and get excited when they lose a lot of weight in the beginning, but as the weight loss slows, they start missing their favorite high-carb treats.

They give up and start eating more and more carbs.

Naturally this makes the diet less effective. It can also lead to a cycle of on-and-off dieting which can disrupt metabolism and stability.

If you are worried about your self-discipline, try a moderate carb reduction first and see if you can stick with that.

Low Carb Works If You Work with It

There is an abundance of compelling scientific research data backing up low carb as an effective weight loss regimen, especially in conjunction with exercise and an overall healthy lifestyle.

When you reduce your blood sugar and your insulin levels and boost protein intake, you improve your metabolism, burn energy faster, and divert that burn away from blood glucose and toward fat stores.

So long as you approach low-carb with realistic expectations and a disciplined attitude, you should see excellent short and long-term results.

If you are ready to get started, be sure to check out our low-carb ​beginners guide.

Do you know of other reasons low carb works? Share them in the comments!

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  • Updated September 28, 2018

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Very informative article Leo! I always feel so much better eating the low carb way and now I know why 🙂

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