As a weight loss strategy, cutting carbs (while reducing the total number of calories by cutting out carbs) has been a dismal failure. Back in 1970 when that charlatan Dr Atkins came out with his unscientific low carb hocum the obesity rate in the United States was 3%. Today, 35% of Americans are obese and it is even higher in the red states that eat high-fat diets.
Here’s the thing, though: Carb reduction costs us.
All human being require significant amounts of healthy carbohydrates to stay healthy
Sure, we can cut carbs temporarily if we need to lose weight quickly but all we will lose is muscle and water weight. For us humans, keeping carbs too low for more than a few weeks will have disastrous consequences. This is especially true for those of us who live active lives.
If you’re sedentary, your carb needs are lower. So you might be able to get away with more restriction but eventually if will catch up to you and damage your brain, liver and kidneys.
If you like to exercise regularly and enthusiastically, restricting your carb intake too drastically will lead to:
- decreased thyroid output
- increased cortisol output
- decreased testosterone (This is why fat men have tits and act so girly)
- impaired mood and cognitive function (This is why people on low carb diet forum and weight loss surgery victims act like such drama queens.)
- muscle catabolism (People on LC diets are weaklings.)
- suppressed immune function (People on LC diets are sickly)
In other words: Your metabolism will slow, your stress hormones go up and your muscle-building hormones go down. You feel lousy, spaced-out, sluggish, cranky… and maybe even sick.
Most vexing of all: You won’t even lose that much weight in the long term and most of it will be muscle. How dumb is that?
Decreased thyroid
In order to function properly and to maintain an appropriate metabolism, our body produces an important hormone called T3. T3 is the most active thyroid hormone and is incredibly important for blood glucose management and proper metabolic function.
Low T3 levels can lead to a condition called euthyroid sick syndrome, in which people are constantly cold and sluggish. (Imagine your metabolic “body motor” idling at a slower speed.)
A landmark study, known as the Vermont Study, found that T3 is very sensitive to calorie and carbohydrate intake. When calories and carbs are too low, your T3 levels drop.
In addition, the Vermont Study found that another hormone, reverse T3 (rT3), is also sensitive to calorie and carbohydrate intake. Reverse T3, as the name implies, inhibits T3.
Getting enough carbs can lower reverse T3. Not eating enough carbs will increase it, thus blocking the important work of T3.
The Vermont Study is far from alone. Other research confirms that ketogenic (ultra-low carb) diets reduce T3 levels as rapidly as starvation.
Additional studies show that when calories are held constant (in this case at 2100 calories), reducing carbohydrates from 409 g to 202 g and then to 104 g significantly reduced serum T3 levels (from 91 to 86 to 69 ng/dL respectively).
Finally, French researchers examined four calorically equal diets (2800 calories in this case), lasting 1 week each. Two of these diets contained 250 grams of carbs, which is a fairly typical proportion. The low-carb diet included 71 grams of carbs, and the high-carb diet included 533 grams of carbs.
T3 levels were equal on the normal and high carb diets (ranging from 163.3 to 169.5 ng/100 mL). However, on the low carb diet they fell to 148.6 ng/100 mL on average. And of course, rT3 correspondingly rose on the low carb diet, but not on the standard or high carb diets.
Thyroid hormones are important for more than just weight loss; they also have profound effects on our overall health and energy levels.
Thus, when you don’t eat enough, and/or eat enough carbs while exercising:
- T3 goes down
- Reverse T3 goes up, further blocking T3
- You feel like crap, and eventually your training sucks
EATING too much fatty food causes brain damage linked to obesity, according to new research. US scientists found a sudden change to a high-fat diet triggered inflammation in a key area of rodent brains responsible for regulating body weight.
The inflammation produced distinctive scarring similar to that seen in stroke patients – and that brain scarring was then observed in humans who were overweight. While the research does not unequivocally prove brain damage caused by fatty food is linked to obesity, it provides strong indications for further research.
“It would be unlikely you could injure that part of the brain and not affect the level of bodyweight because that’s what that area does,” said Michael Schwartz, who is the director of the University of Washington’s Diabetes and Obesity Centre of Excellence.
If you’re active, you need adequate energy and carb intakes for a healthy thyroid.
Cortisol up; testosterone down
Research consistently shows that people who exercise regularly need to eat enough carbs or their testosterone will fall while their cortisol levels rise. This is a sure-fire recipe for losing muscle and gaining fat. Iit’s also is responsible for excessive stress.
In a study in Life Sciences, men who ate a high carbohydrate versus a low carbohydrate diet for 10 days had higher levels of testosterone and sex hormone binding globulin, and lower levels of cortisol.
A few years later, another study took this research a step further. This time the subjects included men and women who exercised regularly. And in addition to considering the effect of their diet on hormones, researchers put them through some performance tests.
Once again, when the subjects ate a low carb diet, their testosterone (and other anabolic hormones) went down, while their cortisol a stress hornone went up.
And, after following a low carb diet for just three days, only two of the six participants were able to complete the cycling test! Meanwhile, when following the higher carb diet for three days, all six participants were able to complete the test.
In 2010, researchers reconsidered the same question — this time in relation to intense exercise. In this particular study, subjects eating the low carb diet (where 30% of their calories came from carbs) saw a drop of 43% in their testosterone to cortisol ratio. Not good. Meanwhile, the control group (who got 60% of their calories from carbs) saw no change in their testosterone/ cortisol ratios.
Thus:
- inadequate carbohydrate intake can decrease testosterone (which no one wants); and
- increase cortisol (which no one wants); while
- negatively affecting performance (which no one wants).
Carbohydrates and women’s hormones
We now know that eating too low-carb for too long can cause significant disruptions to many hormones.
This seems especially true for women, whose bodies may be more sensitive than men’s to low energy or carbohydrate availability (perhaps because of the evolutionary importance of having enough body fat and nutrients to sustain a pregnancy).
While organs like our gonads or thyroid make hormones, Mission Control of our hormone production system is the central nervous system (CNS), i.e. the brain.
Our hypothalamus and pituitary glands, which sit in the brain, are exquisitely sensitive to things like energy availability and stress (which can include life stress and exercise stress).
The hypothalamus and pituitary work together with other glands such as the adrenal glands. This partnership is often known as the hypothalamic-pituitary-adrenal, or HPA, axis.
Thus, when women don’t eat enough calories or carbohydrate — or even when women eat enough calories but not enough carbohydrate — they face hypothalamic amenorrhea.
This means disrupted hormones and stopped — or irregular — periods because of the HPA’s response to perceived starvation and stress.
In hypothalamic amenorrhea, hormone levels plummet, and the cascade is felt throughout the system. You end up with low levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estrogen, progesterone, and testosterone.
In addition, we’ve already seen that not eating enough carbohydrate tends to increase cortisol levels. When cortisol rises, it signals your HPA axis to further decrease pituitary activity. Not good.
Your HPA axis regulates functions such as stress response, mood, digestion, immune system, libido, metabolism and energy levels.
And your pituitary in particular is responsible for synthesizing and secreting growth hormone, thyroid stimulating hormone, prolactin, LH, FSH and other incredibly important hormones.
With all this said, here’s the takeaway message: Many women try to eat low-carb, wanting to be healthier.
Yet because low-carb diets can significantly disrupt hormone production, women with too-low carb intakes — especially active women — can face:
- a stopped or irregular menstrual cycle;
- lowered fertility;
- hypoglycemia and blood sugar swings;
- more body fat (especially around the middle);
- loss of bone density;
- anxiety, depression, and other mental health issues;
- chronic inflammation and worse chronic pain;
- chronic fatigue and disrupted sleep; and
- a host of other chronic problems…
…ironically, this is the exact opposite of what they wanted in the first place.
Muscle loss
When we think about building muscle, we usually think of protein. But research shows that lowering carb intake can affect your muscle mass even if protein remained constant. In other words, even if you’re guzzling protein shakes or eating steak 5 times a day, you could be losing muscle if you aren’t getting enough carbs.
A recent study from the Netherlands compared three diets:
- a high carb diet (85% carbs);
- a medium carb diet (44% carbs); and
- a low carb diet (2% carbs).
All diets had the same total calories and the same amount of protein — 15%. (Yes, a little low, but more or less adequate.)
The result? For starters, pretty consistent with other research.
- T3 levels and reverse T3 levels stayed the same with high and moderate carbohydrate intake.
- T3 levels and reverse T3 went down on the low-carb diet.
But here’s the interesting wrinkle. In this study, the researchers also measured urinary nitrogen excretion to see how the diets affected protein breakdown.
In this case, the low carb diet increased muscle breakdown, because severely low carbs lowered insulin levels.
Again, you’d assume that protein intake would determine muscle breakdown. And you might assume — based on what you’ve heard — that having higher insulin is always “bad”. In fact, insulin is crucial for building muscle.
When you get enough carbs to meet your needs, you replenish muscle glycogen and create an anabolic (building-up) hormonal environment. You get strong and buff. That’s good.
Conversely, when you don’t eat enough carbohydrate, muscle glycogen is depleted and a catabolic (breaking-down) hormonal environment is created, which means more protein breakdown and less protein synthesis. This means slower muscle growth — or even muscle loss.
Putting it all together
The bottom line? Not eating enough carbohydrates can lower T3 levels, disrupt cortisol to testosterone ratios, interfere with a woman’s delicate hormone balance, contribute to muscle loss, and prevent muscle gains.
Definitely not what most of us want!
But wait a minute.
Even if all of this is true, aren’t low carb diets better for fat loss?
And aren’t fat-adapted athletes performing just as well as athletes who eat a lot of carbs?
Low carbs are not better for fat loss
The logic seems so clear and appealing: High carbs lead to insulin which leads to fat storage. Low carbs keep insulin low, which should get you effortlessly lean while you enjoy chicken wings, salmon, eggs, and butter.
Indeed, many people who try low-carb dieting are initially pleased by an immediate weight loss… which is mostly water and glycogen. So, in the short term, it seems like low-carb diets are superior but does long-term evidence support low-carb dieting Research says no. Over the long haul, any differences between low-carb and other diets even out.
Protein: The hidden success factor
Most studies that suggest low-carb diets are superior suffer from a common methodological flaw: They usually don’t match protein intake between groups. This means that the low carb group often ends up consuming significantly more protein.
We know that getting plenty of protein has many advantages:
- protein has a higher thermic effect — our bodies have to “rev up” to digest it (you’ll know this if you’ve ever gotten the “meat sweats” after a big steak);
- protein makes people feel fuller, longer; and
- protein helps people retain lean mass.
In other words, the big “secret” might be a high protein diet rather than a low carb diet.
So let’s play fair and look at a study where protein was matched. In this study, subjects who ate a moderate carb diet (40% calories from carbs) reported significantly better mood, and lost about the same amount of weight as those on a ketogenic low-carb diet (5% calories from carbs).
Actually, the group who ate a moderate amount of carbs showed a small (though not statistically significant) tendency to lose more body fat as compared to those on a low carb diet (5.5 kg vs 3.4 kg in 6 weeks).
Both diets improved insulin sensitivity. However, the ketogenic diet also increased LDL cholesterol and inflammatory markers and subjects who were on it felt less energetic.
Thus, in this study:
- moderate carb eaters felt better
- moderate carb eaters lost about the same amount of weight, maybe even a little more
- both types of eaters improved insulin sensitivity
- the low carb dieters ended up with worse blood work and more inflammation
Makes you wonder why low carb gets so much hype, doesn’t it?Especially considering that a recent review of long-term low carb versus low fat diets — the largest of its kind so far — found that both low carb and low fat diets reduced people’s weight and improved their metabolic risk factors.
In this review, both diets had about the same weight loss, changes in waist circumference, and measurements of several metabolic risk factors (blood pressure, blood glucose, insulin).
Still, it would be great to understand more about what makes low carb diets “work” at all. One recent study asked: Do low carb diets work because they restrict carbs or because they tend to increase protein?
Over the course of one year, the researchers compared four different conditions:
- normal protein, normal carbohydrate
- normal protein, low carbohydrate
- high protein, low carbohydrate
- high protein, normal carbohydrate.
Interestingly, the two groups eating the high protein lost the most weight.
And the real kicker? Varying the levels of fats and carbs seemed to make no difference to body composition.
