Carbs DON’T Make You Fat!
Many people 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.
carbohydrate-insulin hypothesis of obesity (CIHO)
However, nutrition research continually shows that carbs alone DON’T make you fat. The latest clinical trial is no exception.
This was a tightly-controlled, metabolic ward trial, which meant no cheating on the diet.
For 4 consecutive weeks, 16 overweight 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. 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 or 0.5kg 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.
Do Carbs Make You Gain Weight?
Do carbs make you gain weight? It’s evident that restricting carbs is unnecessary to lose weight… But what about gaining weight?
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.
Carbs do not make you fat!
These increases did not differ between the lean and obese subjects either.
Those Who Live Longest Eat A Lot of Carbs
There are still modern day humans thriving on high carb diets too.
In fact, many of them have the lowest rates of metabolic disease and obesity, and live longer than anyone else. The regions where they live – known as Blue Zones – give us valuable insights into the lifetime effects of certain eating patterns.
Blue Zones Eat Lots of Carbs
The Japanese island of Okinawa has the greatest proportion of centenarians (people over 100 years old) in the world. Their diet has always been carb-dense; high in sweet potatoes, legumes and rice to a lesser extent. In fact, a massive 85% of an Okinawan’s caloric intake came from carbs prior to the 1950’s. Sweet potatoes alone accounted for 69%.
More than 65 years later and so many of them are still alive and well. Those from the Greek Island of Icaria also live long and healthy lives, despite a diet high in bread, potatoes and legumes.
Almost 1 in 3 inhabitants lives to be 90 years old, which is 2.5 times the rate of Americans
The world’s longest living populations have diets rich in carbohydrate foods.
But A Low Carb Diet Works For Me?
Low carb works studies show low carb diets can be an effective strategy for weight loss.
Especially if you previously struggled following a low fat diet.
But it’s not because carbs alone made you gain fat. Nor is it because cutting carbs alone made you lose fat.
A reduction in carbs automatically means an increase in protein and/or fat. It’s this entire macro nutrient ratio shift – coupled with an increase in whole (unrefined) foods (complex carbohydrates) that’s responsible for the positive outcome.
Studies show a diet higher in protein keeps you feeling full and tends to decrease overall calorie intake, at least in the short term.
A diet lower in refined carbohydrate (simple carbohydrates) and saturated fats typically found together in junk food also favours a reduction in calorie intake. This is because of how calorie-dense and highly palatable junk foods is.
Then there’s also the loss of water that accompanies carb reduction. Alongside fat loss, this makes the bathroom scales shift favourably, and quickly.
The combination of these factors is why a low carb diet so often leads to weight loss. Replacing refined carbs with protein (and possibly mono saturated fats) can help to consistently curb your appetite and reduce total caloric intake, without relying on willpower.
Many are successful on a low carb diet because it automatically higher in protein, which helps to curb appetite. They also typically eliminate all junk foods, which is where our excess calories come from.