Can you believe that just a few decades ago, fat-free foods were all the rage?

I remember one evening, a very fit friend offered huge bowls of jelly beans and pretzels to visitors as an evening snack. She was so happy to inform us that these foods were “perfectly healthy” because they were fat-free.

Today, however, people are much more wary of carbohydrates than fats. A few months ago, I was hanging out with a different group of health-conscious friends. The evening treat of choice was bacon and chocolate.

Is this progress or a new fad?

I think a few points are indisputable:

• Sugar and processed carbohydrates can ruin cause us to gain weight and ruin our health.
• The human body can subsist without carbs.
• Some of the best parts of our diets, like green veggies and seafood, do not have carbs.

For starters, let’s look at the relationship between carbohydrate intake and the recent obesity crisis. From 1971 to 2000, the intake of carbs increased for both men and women. Starting in the mid-1980’s, obesity started increasing at unprecedented rates.

Many said this correlation was clear evidence that carbs are to blame. However, during the same time frame, the intake of fats and proteins also went up.

Furthermore, in the 1970s and before, people were much leaner, yet men and women still got many more calories from carbs than from fats or proteins. When people were leaner, carbs made up 42 to 45% of their daily calories.

If the carbs were the sole cause of weight gain, then we should also see people on low carb diets losing more weight than those on diets with high or moderate carbohydrate intake.

A pivotal study, published in 2009, answered this very question. In the study, 800 dieters were placed in four equal groups. For two years, one group ate a low-carb diet, one ate a high-carb diet, and the last two groups ate diets with different levels of moderate carbs.

The intake of carbohydrates ranged from 35 percent in the low-carb diet to 65 percent in the very high-carb diet. If carbs were the culprit, the groups eating less should have lost the most weight.

Yet at six months, 12 months, 18 months, and 24 months, all of the groups showed the identical amount of weight loss, waist circumference loss, and fat loss.

But even if carbs are not the clear perpetrators of obesity, why not eat less to be sure? Is it bad to eat too few carbs?

In fact, studies have shown that if you consume too few carbohydrates, you can end up with insomnia, fatigue, and depression.

Why would low-carb diets cause insomnia? We sleep when our bodies make a neurotransmitter, called melatonin. Melatonin is made out of the amino acid tryptophan. When we eat carbs, all of the other amino acids, besides tryptophan, are pulled out of our bloodstream.

Thinning out the competition helps tryptophan enter the brain and make melatonin. Diets that are too low in quality protein provide too little tryptophan. Diets that are too low in carbs keep tryptophan from getting to the brain.

This same lack of melatonin is associated with too little of a mood-enhancing chemical called serotonin. If we have too little serotonin, we are more apt to feel depressed and anxious.

Most of the medications used to treat depression are thought to work because they raise serotonin levels. Carbs raise serotonin and can reduce feelings of depression.

Have you ever worked out really hard and felt awful afterwards? Studies have shown that heavy exercisers who do not get enough carbs will feel more stressed and tired for longer periods of time.

Of course, just because you do need to eat some carbs, a loaf of Wonder Bread a day is not the answer!

Next time, I’ll cover the three rules of carbs: the best types, the best amounts, and the best times of day to eat them.