DrawBacks of a Low Carb Diet

In this post I’d like to share a guest contribution from a good friend and one of my mentors, Joseph Hughes (Fit N Sync). Joe has extensive experience competing in physique competitions as well as coaching many other women and men for physique, figure and bikini contests. He also helps the average individual lose unwanted body fat while following a balanced, sustainable nutrition plan.

Joe helped me prepare my nutrition plan for my first Men’s Physique competitions last year, leading me to a first place victory in my Regional contest and 3rd place at the Provincials, qualifying me for the Nationals. We share the same philosophy regarding flexible dieting, also called If It Fits Your Macros (IIFYM), which relates to tracking your calories and macronutrients (protein, fat, carbs) and eating a variety of foods while meeting your calorie and macro needs, based on your individual goals.


One big aspect of nutrition that Joe really helped me gain a more balanced and evidence-based perspective was related to getting over my “fear of carbs”. Like many fitness professionals I was sucked into the belief that “carbs make you fat”, and that they were basically an unnecessary nutrient that we could do without (or at least consume as little as possible). Once I looked at the evidence and began to consume a healthier amount of higher carbohydrate foods (particularly on my training days), while still meeting my calorie needs, my training progress accelerated and my physique improved. I asked Joe to share some of the myths and facts about low-carb diets with us in this post. Enjoy!

The DrawBacks of Low Carb Diets (by Joseph Hughes)

Joe-Fit-N-SyncLow carb diets have their place in the world medically. Especially ketogenic diets for those with major health issues (ie: epilepsy and various neurological issues). But for fat loss? They work but may not be entirely ideal and we’ll get to covering that in a bit.

We have all heard it before; eat less carbs to lose body fat; eat low fat; eat only this or that. Basically highly restrictive elimination diets. Seems that the dietary changes recommended to us throughout the years haven’t made the impact health professionals thought it would.

My conclusion? We’re simply eating too much, and not exercising enough, with periods of crash dieting. This causes massive weight gain afterwards when eating too much resumes, partly due to metabolic adaptation.

The myth has long since been debunked. But unfortunately some fads stick around long past their welcome.

I’m talking about the low-carb diet myth.

I understand the thought process and why it’s still hanging around. Weight gain is a common symptom of hypothyroidism (yet, so is excessive weight loss), and low-carb diets promote short term weight loss by reducing caloric intake. So it must be healthy for your thyroid, right? Not so fast.

The Birth of Low Carb

More recently than the low-fat craze, people started hypothesizing that if it isn’t the fat that’s causing all these problems then maybe it’s the carbohydrates — in particular processed sugar. We have the Paleo movement, the Keto fad, and various books written on the dangers of sugar. Think of Gary Taubes’ book “Good Calories, Bad Calories”. Tell that to the people of Southeast Asia who have been thriving on a high carb diet for a long, long time. Thus labeling food “GOOD” and “BAD” became mainstream and new eating disorders came into play (ie: orthorexia). I suffered with this for many years after overcoming my obesity stage as a teen.

However, if you dig deeper, you’ll realize that much of the research is cherry-picked and just not scientifically sound compared to current conclusions. Especially for those participating in High Intensity Exercise 4-6 times per week.We have had many clients who we have started to increase their carbs to a moderate level, improve endurance, energy levels, and start to see fat loss start to occur again. I recall doubling the daily carb intake for two of my female clients and both lost a few pounds in the first few weeks. Not what they expected!

Unfortunately we’re all biased, no matter what. Even the smartest, most well-read and studied scientist will be. It’s near impossible to be free of bias due to our own experiences and desires. However, it’s not completely impossible to be very objective and critical, which I will attempt in this article.

This is why you’ll often find people who’ve been successful at losing weight with one method or the other (method being low fat, or low carb, Paleo, Twinkie diet) to be complete zealots for a particular method. I have used them all over the past 2 decades but what I choose for me and my lifestyle (super important point) is carb cycling. Do you have to carb cycle? No absolutely not. We make the foods we love work for us not against us. Once you lean out on a calorie deficit, you then reverse diet to keep the body fat down by adding 50-100 calories every few weeks (depending on how low you dropped your calories). Your metabolic rate will increase back up slowly as the food intake is slowly increased.

Admittedly, some people have been successful in losing lots of weight using a ketogenic or very low carb diet, and were able to keep it off. This is good! But for most, sustaining this protocol becomes a burden. There are many people who’ve tread similar waters and crashed hard.

From what I’ve observed, sticking with a long term low carb diet is mostly impossible, for the majority. Food choices are limited, serotonin levels drop, carb cravings go up and binging and weight gain occur with most, with feelings of guilt to follow. This can open a huge can of worms for your mental and physical health.

At first, on a low carb diet, you go through a transition period of feeling really horrible. It will last a few days, but once you get through it, it’s like a revelation from the creator himself. You feel buzzed, excited and full of energy. Many people change their food choices and no longer see the issues from eating the same foods, which may cause food intolerances that cause fatigue, bloating, joint pain and so on. But then cortisol levels increase and over time the adrenal glands become stressed.

You see a initial drop in in scale weight (water weight) once all the muscle glycogen gets burned up (stored carbs). This is a motivator for most. That is why you see many diet programs with a start up phase with low carbs. It makes them look like they are brilliant and your friend will buy the book because you are seeing such great results. Not all bad but not the whole story.

Roast Chicken Dinner

To Carb or not to Carb

We all need glucose for our most important organ: our brain. If you use your brain, it only makes sense to consume enough carbohydrate to cover the energy demands of your thinking matter.

How much is ideal? that’s up for debate based on your activity level, gender and body size, but from everything I’ve read and studied, I think going below 100g carbohydrates per day is rarely ever a good thing for anyone. It is just not necessary. The only time I would advocate it is if your food choices are extremely high fat for that day and you are trying to stay within a calorie range. (good idea)

Now you may be asking yourself… how can someone do well on a low carb or ketogenic diet if we need glucose for the brain?

Humans are incredibly good at surviving. While the brain needs glucose, you don’t have to eat carbs. You can simply make the sugar you need from ingested protein, or the protein you’re made of (your meat wagon, ala skeletal muscles) via gluconeogenesis. However, this is a highly stressful process. You also can run on ketones.

Since you’re already training hard, and dieting to release fatty acids via a caloric deficit, you’re just adding more fuel to the fire. Stress is stress is stress. It will build up, and bite back eventually.

You may be convinced that carbs would spike your insulin levels and give you diabetes, or that they would lock your body fat away so you couldn’t burn it (ie: You would be a “sugar burner” instead of a “fat burner”), that fat was the “preferred” fuel source of your body, and that all of your Paleolithic ancestors ate “low-carb”. Let’s look at why this belief is a gross over-simplification of the facts.

If you can avoid the dietary stress of gluconeogenesis (conversion of protein to glucose), and actually spare your skeletal muscles from atrophy by simply eating more carbs in place of protein or fat, why wouldn’t you? The energy produced from your protein foods cannot keep up with the demand of an hour training session (carbs are your primary fuel), you naturally burn a slightly higher percent of intramuscular fat calories by being ketogenic (some studies show this) but you may pay the price of losing muscle and slowing down your metabolic rate. Not good for long term results, your thyroid hormone, (fatigue, hair loss) and changing your over all body composition. For more about how low carb dieting affects your thyroid, check out this great interview with Laura by Chris Kresser. Also, studies show it will impede your performance, so you most likely will burn less calories during your workout as well which will counteract the higher percentage of fat maybe being utilized.

On top of that, you will miss out on many health benefits of various fruits and other carbohydrate food options. Eating out, family functions, and your home life become more of a stress. Stress can reduce fat loss. Not good. Want more evidence? Check out these studies!:

What Does The Research Say?

  • Hormonal and metabolic changes induced by an isocaloric isoproteinic ketogenic diet in healthy subjects.


“A significant fall in triiodothyronine and rise in reverse triiodothyronine were observed, while thyroxine levels remained unchanged.”

  • Sucrose substitution in prevention and reversal of the fall in metabolic rate accompanying hypocaloric diets:


“The fall in both resting metabolic rate and triiodothyronine concentration was markedly reduced as compared with values during the carbohydrate-free diet. It is concluded that carbohydrate restriction plays an important role in mediating the fall in resting metabolic rate during hypocaloric feeding.”

  • Active individuals on a low carb diet had a drop in testosterone and an increase in cortisol levels:

Carb controversy: Why low-carb diets have got it all wrong.

When the subjects ate a low carb diet, their testosterone (and other anabolic hormones) went down, while their cortisol went up. This is a sure-fire recipe for losing muscle and gaining fat.

  • A ketogenic diet mimics starvation or fasting, at least from a metabolic point of view:


This means it may limit T3 production and potentially negatively influence metabolism. A number of small scale studies have shown that after a period of starvation, refeeding with carbohydrates – but not with protein or fats – normalized thyroid hormone levels:




In one of the studies, researchers evaluated the effects of restricting carbs at various levels (85, 44 and 2% of total energy intake) on thyroid hormones in 6 healthy male participants. Results found that the high carbohydrate diet had no impact, whereas the very low carbohydrate diet did. It caused decreased T3 levels, increased rT3 and free T4 levels:



Thoughts to Ponder:

We know that the caloric deficit is what matters most for a diet to work properly — meaning you lose fat mass. It’s even more important to keep protein intake sufficient for maintaining muscle. Generally we recommend 0.8-1 gram per pound of Lean Body Mass as a minimum.

With the potential negative consequences of a low carb diet (including drop in metabolism, reduced insulin sensitivity, loss of muscle tissue, lower testosterone levels, decreased performance / training intensity, with an increase in stress hormone levels) it may become clear that this may not be the best nutrition plan to follow long term. Training intensity and frequency is very important. We have seen many women lose body fat with a carbohydrate increase from a previous ketogenic diet, who train intensely 4-6 times per week in the initial metabolism shifting process. They sleep better, they train harder, they see their body respond better.

When it comes to eating more carbs, it can be scary if you’ve had a food phobia in the past. My suggestion is to start slow, track your intake, and gradually increase your carbohydrate intake in a manner that you can easily control, starting with post-workout carbs. Keep in mind that if your fat intake is high, and you want to maintain a caloric deficit, you’ll have to lower fats accordingly. Learn more about flexible dieting for protein (and calorie) requirements and such.

Remember — no single source of macronutrient is the reason you get fat. It’s a caloric surplus over time. If it took you a year to gain 40 pounds of fat, it might take you that long to lose it. At the end of the day, your diet needs to be flexible and sustainable, and it needs to serve your needs for long term adherence to reach your goals.

Your Friend in your fitness journey,

Joe Hughes


CEO of FIT N SYNC Fitness

Author of Finding Balance

Developer of FIT N FLEXIBLE

Personal Fitness Trainer NCSF

Published Fitness Model

SociBook del.icio.us Digg Facebook Google Yahoo Buzz StumbleUpon

Leave a Reply

Your email address will not be published. Required fields are marked *

To prove you're a person (not a spam script), type the security word shown in the picture. Click on the picture to hear an audio file of the word.
Anti-spam image