Jennifer Hanes MS, RDN, LD
Low carbohydrate diets have been frustratingly popular since the 90s. I can remember when popular fad diets skewed from low fat to low carbohydrate in high school. It was revolutionary! Everyone was finally going to be skinny!
I can also remember grumpy moods, stories of “gym bro” freakouts at the gym, and complaints of hair loss from male relatives.
In essence, chronic dieters went from constant grumpiness caused by excessive hunger and cardio in the 80s to constant grumpiness caused by low intake of the brain’s preferred fuel.
Carbs provide fuel to our brain and muscles
Our brains consume a LOT of glucose. An organ that contributes only ~2% of our weight consumes ~20% of our daily glucose intake (in a well-balanced diet). In fact, our brains use approximately 5.6mg of glucose (from carbohydrates) per 100g of brain tissue every minute!
So you can imagine, severely restricting your carbohydrate intake could lead to reduced brain performance. People often report feeling grumpy, tired, and foggy-headed, or confused on a low carbohydrate diet.
In addition to giving us energy, steady moods, and clear thinking, the brain utilizes carbohydrates to make various neurotransmitters that enable us to perform many functions, including learning and long-term memory formation.
Glycogen is stored carbohydrates that are found in the brain, muscles, and liver. When exercising, your muscles have a rapid energy source readily available. They do eventually switch to other sources of fuel when glycogen sources are depleted. Unfortunately, fat is an inadequate source for muscle training, and they will turn to protein first! This means that when you don’t eat enough carbohydrates to fuel your muscles you run the risk of muscle breakdown.
*Side note: this is why low-carb diets initially appear so effective. When you don’t eat enough carbohydrates, your body releases glycogen stores to maintain your ideal blood glucose range. Glycogen is stored with water, so you are losing water and glycogen weight, but not necessarily fat! This effect is temporary. The weight gain people see when stopping a low-carb diet is partially a result of restoring glycogen stores.
Carbs help make “feel good” hormones
In fact, low-carb diets are often associated with fatigue and grumpy moods, sometimes even abnormal aggression.
This all makes sense with a quick biology lesson! Tryptophan (widely known in turkey, but actually present in a wide variety of food) is crucial for many of our feel-good hormones, including serotonin and melatonin. To make these hormones, however, tryptophan has to make it into the brain. And the only way it does this is by using carbohydrates as a carrier. So when our carb intake is too low, they are used for their most vital functions only. And unfortunately, a good mood is not vital to survival. (side note, getting enough carbs also prevents muscle breakdown – so they do play a role in keeping you strong as well!)
But… there is value in other carb sources for a quick boost. Refined carbs can give us a quick burst of energy
While not ideal for overall health, a refined carb source (such as potato chips, cookies, crackers, etc) will provide you a fast, but short-acting energy and mood boost. The need for this boost at 3 pm every day may indicate your lunch isn’t as balanced as it could be, or that you simply need to plan a snack into your routine!
Fiber and other complex carbs keep us full and our guts happy
By now, everyone’s heard of probiotics. Some have even heard of prebiotics, which are the foods the probiotics “eat.”
The probiotic fauna in our gut loves them some fiber and complex carbs! Along with unsaturated fat (from fish, nuts/seeds, olives, and avocado), complex carbohydrates are their preferred source of fuel. A happy gut colony can then indirectly lead to benefits in your mood and energy, though scientists are still determining how large this effect is and how it works.
Fiber also has this awesome ability to “gel up” and take up more space in our stomachs. It then moves more slowly through our GI tract than simple carbs. So we fill up, and stay full longer!
Low carbohydrate intake increases cortisol, the “stress hormone”
Our body perceives low carbohydrate intake as a stressor. Any type of stress can raise our cortisol levels and sour our mood. And this “perceived starvation” can definitely be stressful to our poor confused bodies.
This rise in cortisol is for a reason. When we don’t eat enough carbs, our body tries to “make” glucose from other sources, namely protein stores. Cortisol helps it achieve this. Along with increased appetite and reduced energy levels – meaning, we get tired and pissy.
So what does this all mean?
So we should eat carbs, right? So eating pizza, pasta, and bread all day will fix our mood. Then tack on cake, soda, and candy and we’re golden, right?
Not so much…
We need a balance so that we also make sure we get plenty of protein, healthy fats, and non-starchy vegetables.
Additionally, the quality of our carbohydrate intake matters just as much as the quantity. Carb sources should come primarily from starchy vegetables (yes – even potatoes), fruit, and whole grains.
Those lovely, lovely probiotics don’t love sugar as much as you do! Have your simply carb snacks when the occasional craving strikes. But focus on the sources listed above.
You’ll have more stable energy and carb distribution throughout the day as a result.
For those of you that are more visual, I’m a big fan of Harvard’s Healthy Plate.