Carbohydrates (or “carbs” for short) are nutrients that provide energy for the body in the form of glucose or sugar. There are two types of carbs: simple and complex. Simple carbohydrates (or simple sugars) provide quick energy and can be found in processed form like cookies, candy, and sodas or from natural sources such as fruits, vegetables, and milk or dairy products. Complex carbohydrates are good sources of fiber that come from whole grain breads, cereals, and pasta.

Any extra glucose that is consumed from carbs gets stored in the muscles and liver as glycogen, which is used for energy reserves. Eating food rich in carbohydrates (especially complex carbs) is healthy, but consuming too many carbs results in extra calories that cause fat buildup in the body.

People who adopt a diet that is low in carbohydrates (often called a low-carb diet) gravitate toward foods that have fewer carbs but are richer in protein and fat. Low-carb diets generally include more vegetables, meat, fish, cheese, eggs, and nuts. This type of diet is often chosen with the purpose of losing weight quickly and easily.

When the body digests carbohydrates, blood sugar levels increase. This causes a rise in levels of insulin, which prevents fat breakdown in the body. With a low-carb diet, insulin levels remain lower, so the body tends to use up fat reserves for energy, which results in weight loss.

The rate at which a certain food releases sugar into the bloodstream is measured by its glycemic index (GI), and the glycemic load (GL) accounts for both the GI and the amount of carbohydrates the food provides in a single serving. Low-carb diets incorporate foods with both a low GI and a low GL. As a result, low-carb dieters take in fewer calories and lose weight even though there is no change in the amount of protein and fat intake. However, research has shown that after about six months, low-carb diets are not any more effective than other types of diets.

Though carbohydrates provide quick sources of energy, people who are on a low-carb diet receive a steady supply of energy from proteins and fats. These dieters tend to feel fuller for a longer period of time because the body slowly digests these nutrients. With a low-carb diet, the GI readings of foods are not as important because only a small percentage of the individual’s total calories comes from carbohydrates.

But experts disagree about whether avoiding high GI foods helps with weight loss. Some attribute weight loss from a low-carb diet to the notion that people get bored with the acceptable food options, so they tend to eat less and consume fewer calories. There is also an initial diuretic effect (loss of water weight) associated with low-carbohydrate diets. Many studies indicate that the weight loss from a low-carb diet may not become permanent, and that gaining the weight back after the diet is stopped is very common.

More research needs to be conducted to determine the safety of low-carb diets. If a dieter consistently consumes unsaturated fats, then his or her cholesterol levels may diminish; but an increase in saturated fat consumption can raise cholesterol levels, which increases the risk of heart disease and certain types of cancer. Also, a failure to get enough complex carbs, fruits, and vegetables in a diet may result in low fiber levels, which can lead to constipation or other gastrointestinal problems.

Very low carbohydrate diets (those that call for less than 100 grams of carbs a day) can cause a condition called ketosis (an accumulation of keto acids) due to extensive fat-burning. Small amounts of keto acids are easily excreted by the kidneys, but large amounts in the bloodstream can often cause nausea, fatigue, bad breath, dehydration, dizziness, and abnormal heart rhythms due to electrolyte imbalances. Therefore, people who embrace an extreme low-carb diet must drink plenty of water to help flush the keto acids from the body.

A diet that is rich in meat, milk, and dairy products necessitates the digestion of more protein, which puts a heavier load on the kidneys. Pregnant women and those with heart problems, diabetes, high cholesterol, or kidney stones should consult a doctor prior to starting a low-carb diet.   

Following a low carbohydrate diet may lead to inadequate nutrition. Analyses of these types of diets have revealed deficiencies of vitamins A, B6, B1, C, and E as well as minerals like calcium, magnesium, iron, and potassium.

Therefore, multivitamin supplements are strongly recommended with low-carb diets (along with calcium supplementation for women) as well as additional fiber intake.    

The most important aspect of any diet is to make sure that all nutritional needs are being met. When embarking upon a low-carbohydrate diet, it is better to replace simple carbs with complex carbs that are rich in vitamins and minerals. Also, foods that are labeled “low carb” may contain other ingredients to replace the carbohydrates to the point where they may contain more calories than their traditional counterparts. And when planning a low-carb diet, it is best to focus on fresh foods and those that have unsaturated fats, and to avoid those that are full of saturated fats. Above all, be sure to incorporate exercise into your low-carb diet in order to burn the calories and facilitate the weight loss process.

Low-carb diets can be effective if they provide the necessary nutrients while reducing a dieter’s caloric intake. But it is always a good idea to check with a doctor before starting any weight loss plan.