Science Confirms It: Carbs Don’t Make You Fat, This Does

by - September 17, 2019

Science Confirms It: Carbs Don’t Make You Fat, This Does

Cutting carbs is the most important change for weight loss.

At least, that’s the idea sold by Gary Taubes, Dr. David Ludwig and other low carb enthusiasts.
They believe carbohydrate drives obesity because it raises the hormone insulin. Insulin is said to block the release of fat and also drive additional fat storage.
However, nutrition research continually shows that carbs alone DON’T make you fat. The latest clinical trial is no exception.

You might’ve already seen my stance on this. But let’s put our personal food ideologies aside for a moment to honestly consider the weight of evidence available.

Cutting Carbs Does Not Increase Metabolism or Fat Loss
If raised insulin drives weight gain, then conversely, reduced insulin (from cutting carbs) should be therapeutic.
In other words, we’d expect an extremely low carb diet to cause more fat loss than a typical Western diet.

The latest trial to compare these two eating patterns – ironically funded by Taubes’ own NuSI organisation – indicates this is not true.

Study Design
This was a tightly-controlled, metabolic ward trial, which means no cheating on the diet.

For 4 consecutive weeks, 16 overweight or obese men were fed a standard American diet, quite high in carbs (50% Carbohydrate, 15 % Protein, 35% Fat).

According to the sample menu published, it included loads of refined carbs including lemonade, granola bars, pretzel sticks and sandwich bread.

Participants were then immediately switched to a very low carbohydrate, ketogenic diet (5% Carbohydrate, 15% Protein, 80% Fat) for another 4 weeks (1).
Both the high carb diet and the ketogenic diet were equal in calories and protein, and they had no access to any outside foods for the entire 8 week period. Participants also rode an exercise bike for 30 minutes daily.
Changes in energy expenditure, body composition and relevant blood markers were recorded each day using the gold-standard methods where possible.


After the first 4 weeks on the high carb diet, participants lost 1.1 lbs  (0.5 kgs) of body fat on average.

Switching to the low carb diet for the remaining 4 weeks led to a dip in insulin levels by almost half. However, once again participants lost just 1.1 lbs of body fat.
So there was no difference between eating patterns on fat loss despite the difference in insulin, effectively disproving the carbohydrate-insulin hypothesis.

Switching to the low carb diet did cause an initial sharp decrease in total weight loss, but this was due to the drop in water weight that accompanies carb restriction (2).

Source: Smart Training & Flexible Dieting

To be fair, the low carb diet did increase metabolic rate by 57 calories per day on average. This outcome was actually the main aim of the study.

However, this number started much stronger before plummeting down to about 40 calories per day, which is clinically insignificant. In fact, the metabolic advantage all but disappears after several weeks.

Some will say that 40 calories x 365 days per year = 14,600 calories per year. This equals 4.1 lbs (2 kgs) of weight loss in a year, assuming a 3,500 calorie deficit equals 1 lb of fat.

But it doesn’t actually work like that. A daily deficit of 40 calories is likely to equal only 4 lbs of weight loss after 2-3 years, if you don’t cheat.

Is that worth cutting your diet to strictly 5% carbs?

Summary: A well-designed clinical trial, funded by low carb advocates, found a low carb ketogenic diet was not beneficial for fat loss or metabolic rate. The high carb diet was just as effective – if not better – for body fat loss, despite the higher insulin levels.

Other Trials Show No Advantage From Cutting Carbs
This was not the first well-controlled clinical trial to show cutting carbs has no advantage for fat loss.

In fact, it was shown over a decade ago.

In a 6-week trial of 20 subjects randomly assigned to follow either a ketogenic diet (5% carbs) or a moderate carb diet (40% carbs), there was no difference in average weight loss, fat loss or insulin changes. All food and beverages were provided to participants (3).
Average change in body mass and fat mass in ketogenic diet (▪) and nonketogenic (○) diet groups during the 6-wk feeding trial and at the week 10 follow-up.

If anything, strictly cutting carbs leads to less fat loss as time goes on. Subjects also reported the ketogenic diet was worse for feelings of energy and overall mood.

There was also a smaller and slightly different version of the above NuSI study, also run by Dr. Kevin Hall.

His team found a reduced carb diet (29% carbs) resulted in less fat loss than a reduced fat diet (7.7% fat). At the time, their computer model even predicted the trend seen in the latest study (4):

Change in fat mass of reduced fat vs reduced carb. Source:

Although the reduced carb diet (29% carbs) was not quite “low carb”, it still lowered insulin levels considerably. Despite this change there was no fat loss advantage.

Summary: Several other well-controlled trials looking at the fat loss effects of reduced carb and very low carb ketogenic diets indicate they are not beneficial for long-term fat loss.

 Do Carbs Make You Gain Weight?

It’s evident that restricting carbs is unnecessary to lose weight… But what about gaining weight?
Is overeating carbs worse than overeating fat, as per carbohydrate-insulin hypothesis?

This has also been well-studied, and clinical trials show this is not the case, per unit calorie.

In a study of 16 men (9 lean and 7 obese), subjects were fed a strict diet providing 150% of caloric requirements (designed for weight gain). The additional 50% of calories came from either carbohydrate or fat for 14 days at a time. Subjects completed both diets in a crossover design.

Researchers found that both carbohydrate and fat overfeeding caused almost identical increases in body weight, fat mass, and lean mass (5).
These increases did not differ between the lean and obese subjects either.

Another similar overfeeding study of 20 lean men also found no differences in the increase of total weight or fat mass gained after 21 days (6).

It appears when calories are matched, there’s no difference in fat gain between overeating carbs or fat.

 What About When We Don’t Overeat?
Do carbs influence body fat in individuals who are not overeating calories?

Apparently not.

In a series of tightly controlled clinical studies, 15 subjects were fed a diet that shifted greatly in the amount of carbs or fat it contained over a 13-week period. The calorie amount was for weight maintenance (no gain or loss), and was kept the same regardless of the carbohydrate-to fat ratio (7, 8).

This is how one subject’s weight tracked throughout the study. The first 38 days were high carb (75% carbs), the remaining were low carb (15% carbs).
The researchers concluded, “The carbohydrate-to fat ratio could vary widely with little or no alteration in the energy requirement for weight maintenance.”

Therefore, if you aren’t consuming excess calories, weight stays the same regardless of the amount of carbs you enjoy.

Summary: Clinical studies show that eating carbs instead of fat makes no difference to body fat, as long as total calories remains the same. This holds true whether we overeat calories or not.

Indigenous And Pre-Industrialised Populations Thrived On Carbs
Still  not convinced that carbs are not uniquely fattening?

Even if we have a tendency to ignore the clinical studies (the most powerful proof available), the carbohydrate-insulin theory doesn’t match the historical and data-based proof.

Indigenous teams just like the Tarahumara Indians, Kitavans and Massas all thrived on high carb diets for many years. avoirdupois was rare (if not non-existent) all told of those endemic teams (9, 10, 11).

For example, Kitavans had just about no overweight folks – and extremely low internal secretion levels – despite a diet that was seventieth carbs (12).

Kitavans (source:

The same was ascertained for pre-industrialized Asian populations up till the twentieth century, living on staple foods like rice, noodles, potatoes and fruit (13, 14).
Even by the 1990’s, 50-60% of calories ingested in Japan and China still came from carbs. This was over the North American country or United Kingdom, nevertheless avoirdupois rates were abundant lower (15).

If carbs themselves ar finished, these populations wouldn't have had lean bodies and physiological state overall, no matter however active they were.

Taubes’ counter argument is that avoirdupois wasn't uncommon in several native populations from the 1950’s onward. However, by now several developing nations and endemic teams – like the Pima Indians – already had access to subtle, reasonable (often subsidised) Western food.

Summary: There ar various historical samples of populations that remained slim and healthy consumption high carb diets. this means carbs themselves aren't finished. endemic teams solely became weighty when the introduction of Western food.

Those Who Live Longest Eat a great deal of Carbs
There ar still modern-day humans thriving on high carb diets too.

In fact, several of them have all-time low rates of metabolic sickness and avoirdupois, and live longer than anyone else. The regions wherever they live – called Blue Zones – offer North American country valuable insights into the lifespan effects of bound consumption patterns.

The Japanese island of Okinawa has the best proportion of centenarians (people over a hundred years old) within the world.

Their diet has continuously been carb-dense; high in sweet potatoes, legumes and rice to a lesser extent. In fact, a vast eighty fifth of AN Okinawan’s caloric intake came from carbs before the 1950’s. Sweet potatoes alone accounted for sixty nine (16).

More than sixty five years later and then several of them ar still alive and well.
Those from the Greek Island of Icaria conjointly live long and healthy lives, despite a diet high in bread, potatoes and legumes.

Almost one in three inhabitants lives to be ninety years previous, which is 2.5 times the speed of usa citizens (17).
Other Blue Zone regions share similar dietary traits to the Okinawans and Icarians, therefore it’s not simply a freak coincidence.
Granted their active lifestyles may be a issue to their longevity, however a high sugar diet doesn't cause them to induce fat or sick.

Summary: The world’s longest living populations have diets made in sugar foods.

But an occasional Carb Diet Works For Me?
Studies show low carb diets may be a good strategy for weight loss.
Especially if you antecedently struggled following an occasional fat diet.

But it’s not as a result of carbs alone created you gain fat. neither is it as a result of cutting carbs alone created you lose fat.

A reduction in carbs mechanically means that a rise in supermolecule and/or fat. It’s this whole nutrient magnitude relation shift – let alone a rise in whole (unrefined) foods – that’s accountable for the positive outcome.

Studies show a diet higher in supermolecule keeps you feeling full and tends to decrease overall calorie intake, a minimum of within the short term (18, 19, 20).

A diet lower in refined sugar and fat – usually found along in food – conjointly favours a discount in calorie intake. this can be owing to however calorie-dense and extremely comestible junk foods is.

Then there’s conjointly the loss of water that accompanies carb reduction. aboard fat loss, this makes the toilet scales shift favorably, and quickly (2).

The combination of those factors is why an occasional carb diet therefore usually results in weight loss. substitution refined carbs with supermolecule (and probably fat) will facilitate to systematically curb your craving and cut back total caloric intake, while not wishing on possession.

Summary: several ar fortunate on an occasional carb diet as a result of it mechanically higher in supermolecule, that helps to curb craving. They conjointly usually eliminate all junk foods, that is wherever our excess calories come back from.

No, Carbs Don’t cause you to Fat
The science is in.

Carbs are not any worse for your waist than the other nutrient.

Studies show that once low carb and high carb diets ar matched for calories, there's zero distinction to body fat modification. Regardless if your total caloric intake is excessive or not.

This is sensible considering all the past and gift populations that thrive on high carb consumption patterns.

That’s to not say carb-laden junk foods and soft drinks ar off the hook. These merchandise ar low in nutrients and don't cause you to feel full or happy. they're beyond question the most important contributors to excess calories, and thus one in all the most drivers of avoirdupois and connected health issues.

But it’s owing to food as an entire – the full calories – and not simply the carbs.

If you get pleasure from an occasional carb consumption pattern and it’s improved your health then there’s no reason to prevent. it should even be superior to low-fat for managing polygenic disorder.

But there’s no have to be compelled to cut carbs to extremes, like a ketogenic diet.

And simply recognize that cutting carbs is certainly not the sole thanks to be healthy or lose weight…

So stop telling folks it's.

A version of this post originally appeared on Diet vs sickness as Science Confirms It: Carbs DON’T cause you to Fat

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