Eating Too Few Calories

Your Metabolism

Metabolism pertains to the biochemical reactions within the body that produce energy and sustain the processes necessary for life. These processes involve breaking down food into nutrients the body uses for energy, growth, and repair. Consuming insufficient calories can reduce your metabolic rate and result in health problems due to inadequate nourishment. A person's minimum calorie intake varies depending on factors such as age, sex, weight, height, and activity level. However, a general guideline is that men should not eat less than 1500 calories per day, and women should not eat less than 1200 calories per day. As discussed below, some issues could arise from consuming fewer calories than recommended.

Harder to Lose Weight

When you eat insufficient calories, your body will decrease its metabolic rate to conserve energy, making weight loss more difficult. The decrease in metabolic rate and slower calorie burn can happen even when attempting to lose weight while being overweight. A lowered metabolism may continue long, even after going off the diet.

Loss of Muscle Mass

The body may break down muscle tissue to get the extra energy it needs. A decrease in muscle mass can also lead to a decrease in metabolism because muscle tissue is more metabolically active than fat tissue, meaning it burns more calories at rest than fat. Muscle tissue accounts for a significant proportion of daily calorie expenditure. When muscle mass decreases, less energy is needed to maintain the remaining muscle tissue. As a result, people with less muscle mass may find it more challenging to lose weight and maintain weight loss since their bodies require fewer calories to function compared to someone with a higher proportion of muscle mass.

Hormone Imbalance

Your metabolism also plays a role in producing various hormones, such as thyroid hormones. Decreased metabolism can lead to these hormones' imbalances and related health issues.


Consuming too few calories can make meeting your daily nutritional needs more challenging. The diet's lack of essential nutrients ( protein, vitamins, and minerals) can lead to fatigue and health problems. A slower metabolism also means your body is less efficient at converting food into energy, which can decrease energy levels.

Hair Loss

Riboflavin, biotin, folate, and vitamin B12 deficiencies have been associated with hair loss. If your body doesn't receive enough of these nutrients, it can lead to hair loss. Also, sudden changes in weight due to dieting can cause temporary hair loss called telogen effluvium.

Reduced Fertility

Women severely restricting their calorie intake can experience disruptions in their menstrual cycles, making it more difficult to conceive. In men, it can reduce sperm count and motility and lower testosterone levels, reducing fertility.

Weakened Bones

Your body may reduce the production of certain hormones, including estrogen and testosterone, essential to bone health. Also, calorie-reduced diets are usually lower in calcium and other bone-healthy nutrients, which can decrease bone mass.

Lowered Immunity

An immune system that works optimally requires a well-balanced and nutritious diet. When you don't consume enough calories, your body may not get the nutrients it needs to support immune function, leading to decreased infection resistance and longer recovery times from illnesses.


A lack of nutrients, such as magnesium, due to consuming too few calories can also contribute to sleep problems. Magnesium is essential in critical bodily functions, including regulating sleep. It helps regulate melatonin production, a hormone that promotes healthy sleep-wake cycles. Magnesium also helps regulate the neurotransmitters responsible for calming the brain and reducing anxiety, leading to better quality sleep.


You may not get enough fiber when you consume little food, which is crucial for maintaining regular bowel movements. Also, when you eat less than the amount your body needs to function correctly, the body saves energy by slowing the digestive process and reducing bowel movements, which can cause constipation.

Feeling Cold all the Time

A slowed metabolism can decrease your core body temperature, making you feel cold. Your body may also divert blood from your extremities and towards your vital organs, making you feel cold, particularly in your hands and feet.

In conclusion, it is essential to consume enough calories to fuel your body and provide it with the necessary nutrients to maintain optimal health. It's always recommended to seek personalized guidance on your unique dietary requirements from a healthcare professional or a certified dietitian.