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Low Carb Diets: Truth or Trend

By Terry Passano, RDN, LDN, CLT – University Dietitian

Welcome to spring 2023!

I often have people come to me who have started or want to start a “diet” to manage their weight and eating habits. Often, they want to eliminate a big swatch of foods or avoid eating to an extreme. The diet I am most often asked about is the low-carb diet. Today, we will focus on what makes up the low-carb diet, its pros and cons, and alternative approaches to managing weight and health risks.

Have you heard of, or maybe considered, a low-carb diet? There continues to be a lot of online buzz about this.

Some say they are amazing for weight loss. Others warn that they can increase your risk of heart disease.

So, what is it?

Low-carb diets may help some people lose weight and/or manage their blood sugar levels. And they may do these (slightly) better than low-fat diets.

Let me help you figure out what exactly a low-carb diet is and whether it's something you should consider… or not. We will explore low-carb eating and other approaches to improving weight and health.

What are "carbs" (and are they bad)?

No, carbs aren't inherently bad (more on this below).

Carb is short for carbohydrate. Carbs are one of the three main macronutrients in the diet. Macro, as in large, means they're the large components of your diet. Just like protein and fat, carbs give us the energy (calories) we need to function over the day. Most foods contain two, if not all three, of these essential macronutrients.

Carbs are definitely part of a healthy diet. Not only are they easily converted into the energy we all require, but they're found in many foods full of other nutrients like essential vitamins, minerals, fibers and phytonutrients. Like fats and proteins, carbs can also be found in nutrient-poor, low-quality foods.

Medline Plus says: "It is best to get most of your carbohydrates from whole grains, dairy, fruits, and vegetables rather than refined grains. In addition to calories, whole foods provide vitamins, minerals, and fiber."

Whole foods also provide us with phytonutrients which provide beneficial information to our body to support our good health. The fibers in grains, fruits and vegetables support a balanced and robust microbiome. Avoiding these foods can negatively affect our microbiome. A healthy microbiome is essential for a healthy body and mind.

Similarly to other macronutrients, carbs have calories. Eating or drinking too many carbs can provide excessive calories – this is especially detrimental if they're from foods that are not rich in other nutrients, are from highly processed foods or contain unhealthy fats.

The effect of different carbs on your health

Carbs come in three different shapes and sizes:

  • Sugars (found in juices, dairy, sodas, desserts, etc.) are the smallest and are the primary type of "fuel" used by your body for energy. Fruits also contain a good amount of sugars.
  • Starches (found in potatoes, grains, legumes, etc.) are broken down into sugars which then go on to be used for energy. They may also contain fiber.
  • Fiber (found in legumes, vegetables, whole grains, nuts, fruit, etc.) provides bulk that helps us feel full and feeds our friendly gut microbes. Whole fruit has beneficial fiber; however, juices generally do not.

Different types of carbs have slightly different effects on your body. For example, sugars include, not surprisingly, the least healthy form of carbs, such as cakes, cookies, processed foods, and sweetened drinks like soda and lemonade. When you ingest sugars, they're absorbed quickly and can cause a "spike" in your blood sugar level. Sugar also tends to be found in highly processed and less nutritious foods. People who eat more sugar have a higher risk of developing diabetes, heart disease, obesity, and dental cavities. Sugary, highly processed foods contribute to chronic illness both by taking the place of more nutritious foods and by creating an environment that supports the development of chronic disease.

Starches take a bit more time to be broken down into sugars, so their effect on your blood sugar level is slower and lasts longer. This is a better option.

Many starchy, complex carbohydrate foods contain fibers beneficial to the microbiome. These fibers feed the microbes that support our immune system and good health.

Fibers, on the other hand, aren't digested by us but rather help us feel full and contribute to a healthy gut by feeding our friendly gut bacteria. People who eat a lot of fiber tend to have a lower risk of heart disease, stroke and digestive issues and a more diverse and balanced microbiome. Fiber is found in whole grains, fruits, vegetables, and legumes (beans and lentils). These foods are heavy hitters in the Mediterranean diet, which has been shown to improve mood and prevent chronic disease.

Possible benefits of low-carb eating

Low-carb diets may have a slight advantage for weight loss when compared to low-fat diets. However, studies find that after 12 months, the benefits are not that large.

Low-carb diets may help some people better manage their diabetes, high blood sugar, metabolic syndrome, and heart disease. They may also help improve cholesterol and blood lipids, too.

These benefits may occur not specifically from eating fewer carbs but rather because of the quality of food choices when eating a low-carb diet, as well as from losing some weight.

What is a low-carb diet?

Low-carb diets emphasize eating more of the other two macronutrients: protein and fat. This means more meat, poultry, fish and eggs. It also includes non-starchy vegetables.

The amount of carb-rich foods would be reduced, although not eliminated. This means eating fewer desserts, grains (breads, pasta), fruits, sweetened drinks (soda, sports drinks, lemonades, juices, fruits), starchy vegetables, and legumes.

How low the carbs go isn't set in stone or even universally agreed upon. A typical low-carb diet would recommend no more than 50-150 grams of carbs per day. This contrasts with the Dietary Guidelines for Americans, which recommends about 225 grams daily from carbs.

Should I consider a low-carb diet?

Studies show the overall quality of a food or diet is more important than focusing on just one nutrient, like carbs.

A few things to consider:

First, know that if you're trying to lose weight, low-carb is one of many options that can help you – at least for a short time. Finding the right approach for your genes, metabolism and lifestyle may take experimentation. It can be challenging to stick to an eating style long-term, so finding one that works for you is key. What works for your best friend or sister may not work for you. Everyone's preferences and biochemistry are different.

Eating fewer grains (e.g., bread, pasta), fruits, starchy vegetables, and legumes may negatively affect your microbiome. These foods provide resistant starches, which serve to feed the good bacteria in our gut microbiome. They also contain essential vitamins and minerals.

However, it also means eating fewer french fries and other fried foods as well as fast foods, donuts, cookies, cakes and chips. These are heavy contributors to the excess calories we consume and may negatively affect our mental health and contribute to the development of chronic disease. Significantly, these low-carb, high-fat and nutrient-poor foods are also avoided on a low-fat diet.

Be careful when you restrict any major food group, like carbs, for example. This is because you may be restricting essential vitamins or minerals. This can lead to deficiencies and long-term concerns like bone loss, gut problems, and chronic diseases.

Because low-carb diets are restrictive and may not provide all necessary nutrients, this diet isn't recommended for adolescents or pregnant or breastfeeding women.

Most of the research on low-carb diets is short-term, so we don't know all the possible health effects of eating like this over many months or years. It's possible that by eating too much animal proteins and fats, you may increase your risk of heart disease and certain cancers.

If you restrict carbs too much, you can change your body's metabolism and put it into ketosis. This is because your body uses glucose as its primary energy source, so when you don't get a minimum amount of carbs, your body's metabolism changes to start using fat as its energy source. This transition can be challenging and difficult to maintain. It is not for everyone

If you end up craving carbs or other foods, are experiencing gut issues or other bothersome symptoms, or simply don't enjoy eating anymore, a low-carb diet may not be the best for you.

Alternatives to a low-carb diet

The Mediterranean-style diet has been shown to reduce weight and improve physical and mental health. It is an eating style that repeatedly does well in studies. It focuses on eating beneficial carbs rather than highly processed foods, encourages physical activity, and enjoying meals with friends. It has a balance of healthy fats, colorful fresh and local vegetables and fruits, whole grains, and a combination of plant and animal proteins. See the link below for more on the Mediterranean diet, including recipes, meal plans and other information.

Awareness of your eating is essential in any weight management approach. This includes cueing into hunger and fullness and eating the correct foods in the appropriate amount for you. Mindful eating and Intuitive eating can help with this, although they are not specifically focused on weight loss. Look for more on intuitive and mindful eating in our March newsletter.

Portion control is essential in any eating plan.

Macronutrient nutrition tips

Remember, there are healthy and not-so-healthy carbohydrates, fats and proteins. Make sure to choose quality foods containing essential vitamins and minerals more often and highly processed foods less often.

As for proteins, it's best to get them from poultry, fish, dairy, eggs, nuts and beans, and less from red meats like pork and beef. Avoid processed meats such as cured meat, hotdogs, and fast foods. Eating less fried and highly processed meats supports everyone's health.

Regarding fats, focus on foods rich in omega-3s and unsaturated fats and choose less saturated, hydrogenated, or highly heated fats such as fried foods. Healthy fats contain the essential fatty acids needed for soft, supple skin, immune function and brain health. They are found in nuts, seeds, olives, olive oil, avocado and omega-3- rich foods such as salmon, mackerel and other cold-water fish.

If you make drastic changes to your diet, you may experience headaches, fatigue, muscle cramps, skin rashes and digestive upsets. Keep an eye out for these and consult an expert if you experience them.

Bottom line

Harvard Health says: "The best diet is the one we can maintain for life and is only one piece of a healthy lifestyle. People should aim to eat high-quality, nutritious whole foods, mostly plants (fruits and veggies), and avoid flours, sugars, trans fats, and processed foods …"

We are surrounded by food everywhere we go. We eat for social and mood reasons. The foods we choose are influenced by taste preferences, budget, convenience, and health. Finding your personal eating style that supports your brain, mood and body can be challenging. Many of us give up, not realizing that one or two small changes could make a world of difference to our quality of life, in the moment and in the future.

Finding the perfect "diet" does not lie in the latest trend. It involves listening to your body, knowing what it requires and making the best choices for yourself.

Changing your diet or lifestyle to reach health goals is something I specialize in. If you're considering diet changes, book an appointment with me to see if my service can help you.

Links to Check Out

Five Things to Know About Your Microbiome
How to Make Your Belly Happy
Mediterranean Diet Basics

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Harvard Health. (2018, April 9). Which diet is best for long-term weight loss? Retrieved from

Harvard Health. (2018, November). Both high-carb and low-carb diets may be harmful to health. Retrieved from

StatPearls [Internet]. (2019). Physiology, Carbohydrates. Retrieved from

Harvard Health. (n.d.). Low fat, low carb, or Mediterranean: which diet is right for you? Retrieved from

Harvard Health. (n.d.). Going low-carb? Pick the right proteins. Retrieved from

Mayo Clinic. (2017, August 29). Weight Loss. Retrieved from

Medline Plus. (2018, January). Carbohydrates. Retrieved from