How Low-Calorie Diet Is Too Low?

low-calorie diet

The typical American diet is composed primarily of carbohydrates. If you are considering a low-carb diet, reducing the largest source of calories in your diet may feel like a challenge. In addition, understanding how many carbohydrates are in a low-carb or low-calorie diet is not easy.

Before changing your diet, it’s helpful to gather important information – such as the amount of carbohydrates you need and the best choices for healthy carbohydrates. The answers to these questions can help you determine the best nutrition plan for you.

Calories and Weight Loss: What’s the Relationship?

It is well known that eating fewer calories leads to less weight (while eating more calories has the opposite effect) – but why exactly is this? It helps to understand that calories are energy, and that energy plays multiple roles in the body.

When you consume calories as a source of energy, your body will use most of those calories to maintain your basal metabolic rate (BMR), or for biological processes such as keeping your internal organs running, and your body will also use some of that energy to digest the food you just ate (called the thermic effect of food or TEF). The remaining calorie intake should provide energy for your daily activities, or activity energy expenditure (AEE).

The problem is that when we consume more calories than our bodies can use for these processes, there are only so many places they can go. With extra energy left over, that surplus is stored for later use. This storage is either glycogen or fat storage.

Various factors influence how quickly each person’s body metabolizes calories. Medical conditions, genetics, and age can all affect how quickly you reach a caloric deficit or surplus. Different types of foods may also be processed differently. Calories from proteins and complex carbohydrates take longer to digest, so you have more time to burn those calories. With foods high in sugar, these calories are absorbed quickly, which means you may store them as fat rather than using them for energy.

How Many Carbs Should You Cut?

Most of the low-carb diet ads you see suggest limiting your carbohydrate intake well below the government recommended guidelines. And when you see headlines in the news about low-carb diets, the low-carb diets studied tend to be much lower in carbohydrates.

For example, in one large dietary study, researchers defined a low-carb diet as any diet that allowed a maximum of 60 grams of carbohydrates per day. Another study described a low-carb diet as less than 40 grams per day.

Confused? You’re not alone. There is no universal definition of a low-carb diet. Instead, low-carb diets are sometimes defined in terms of grams of carbohydrate consumed, while other times they are considered as a percentage of total caloric intake.

A low-carbohydrate diet is generally defined as a diet containing 20 to 70 grams of carbohydrate per day. Very low carbohydrate diets contain less than 20 grams of carbohydrates per day.

How a Low-Calorie Diet May Help or Harm Weight Loss 

Low-calorie diets are a straightforward, research-proven pathway to weight loss, and there are many journals, calculators, apps and other resources available to calculate your progress. In addition, a standard low-calorie diet plan usually doesn’t restrict any particular foods (or their timing), so it can be a flexible alternative to certain fad diets that tell you exactly what and when to eat.

That said, a slam-burn approach to calories can have its drawbacks. For some people, meticulously tracking numbers and portion sizes can be unhealthy territory that can ultimately lead to dysfunctional eating behaviors. If you have a history of eating disorders or a problematic relationship with food, it’s best to approach calorie counting with caution; if possible, ask a therapist or registered dietitian to help you.

Regardless of your mental health history, an ultra-low-calorie diet may not be sustainable in the long term. For most people, calorie reduction alone is not the answer to lifelong success in maintaining an ideal weight. It also takes introspection, mindfulness, and some sort of physical activity to make the process successful. In fact, an April 2018 study in Obesity Science & Practice found that improvements in mental health over 12 months were associated with greater weight loss success. And a large body of research supports the idea that physical activity enhances weight loss by burning more calories.


Low-carb diets are one type of diet plan, and they may not be suitable for all people. No matter which type of diet you choose, you will need to create a caloric deficit to lose weight. Choosing to restrict one macronutrient is not a foolproof way to lose weight and may lead to unnecessary restrictive eating practices. Be sure to discuss your choices and concerns with your doctor.

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