Fatigue While on a Calorie Restricted Diet

Make sure to set modest goals so that you have enough energy.
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Calorie-deficit fatigue is a common side effect of overzealous dieting. In the quest to lose weight, try to set modest goals so you'll eat enough to provide for your energy needs.


Warnings Against Crash Diets

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Much more research is needed to assess the safety and efficacy of calorie-restricted diets, cautions the National Institute on Aging. It's important to consume a safe level of calories, so consult your doctor before starting on one of these eating plans.

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Read more:Everything You Need to Know Before Trying a 1,000-Calorie-a-Day Meal Plan

According to the American Academy of Family Physicians, restricting daily food intake to less than 1,200 calories for women and 1,800 calories for men may lead to malnutrition. In addition, it's counterproductive because losing weight too quickly will likely result in regaining the lost pounds.

Harvard Health Publishing warns that ingesting less than the minimum daily recommended calories will cause calorie-deficit tiredness. The institution advises against going on crash diets because they deprive you of nutrients and don't supply enough calories to meet your energy requirements.


Low-Calorie Diet Health Effects

Your body requires energy for all biological functions, such as breathing, digesting food and pumping blood, as well as for all physical activity, notes the Academy of Nutrition and Dietetics. In fact, the amount of energy used at rest, called resting metabolic rate, accounts for most of your energy expenditure. When you don't eat enough food, you can experience calorie-deficit tiredness and other adverse health effects.


When your calorie intake is inadequate, your body gets energy from breaking down muscle to release stored energy called glycogen. Your metabolism also slows to conserve energy. Consequences include feeling cold and sluggish and experiencing digestive problems like constipation.

Because the brain needs glucose to function, another effect of cutting calories too much is mental sluggishness. Also, the fast weight loss resulting from having a diet that is very low in calories may lead to abdominal pain and gallstones.


Other adverse effects include vitamin and mineral deficiencies. For example, calorie-deficit diets are often low in vitamin E, which is needed for the immune system to protect against cancer and other diseases. Such diets also tend to have insufficient calcium intake, which leads to osteoporosis and an increased risk of bone fractures.


The Nutrition Council of Oregon describes yet more effects of excessive calorie restriction. The practice causes the muscles to become smaller, which makes walking and all other activities more difficult. Wound healing is also impaired.


Severely restricting calories is downright dangerous. Any diet that limits calories to less than 800 calories per day may lead to a sobering host of ills, states Michigan Health and Wellness. Aside from fatigue, these include weakness, heart irregularities, headaches, decreased metabolism, kidney infections, constipation, diarrhea and loss of lean body tissue. This restriction can even lead to sudden death.

Read more:How Many Calories a Day Is Considered Starving?


Avoiding Dieting Tiredness

If you're on a calorie-restricted diet, take care to eat enough carbohydrates. Because these nutrients are the body's main source of energy, an eating plan that is deficient in carbohydrates leads to dieting tiredness or fatigue, says Virginia Tech. Proteins and fats aren't as efficient as carbohydrates in supplying energy.

Instead of eating three large meals per day, eat small, frequent meals to give the brain a steady supply of nutrients, advises Harvard Health. A few nuts or a piece of fruit can refuel the brain and help prevent sluggishness.


The Academy of Nutrition and Dietetics advocates eating well-balanced meals for optimal energy. This include fruits, vegetables, lean meat, whole grains, low-fat dairy products and a small amount of healthy fat.

When you don't drink enough fluids, one of the first symptoms is tiredness. Water is vital for health because it transports nutrients to cells and removes waste products. To stay hydrated, drink plenty of water during the day as well as before, during and after a workout.


Since food provides energy, and exercise increases energy expenditure, be sure to eat enough to fuel workouts. Eat before, during and after physical activity.

MedlinePlus suggests following a healthy plan like the Mediterranean diet or DASH diet instead of going on a low-calorie diet to lose weight. While these nutrition-dense diets are beneficial for people with certain health problems, they also promote weight loss and include enough calories not to produce dieting tiredness.

Food and Beverages to Avoid

Just as certain foods and beverages boost energy and promote health, certain dietary items make you tired. Don't drink sugary beverages or energy drinks: they give a temporary energy boost followed by an energy crash. Limit your intake of desserts for the same reason.

Alcohol has a sedating effect, so avoid a cocktail with lunch to prevent afternoon drowsiness. Likewise, refrain from a cocktail at the close of the workday if you want to have energy to pursue a hobby in the evening, suggests Harvard Health Publishing.

Benefits of Calorie Restriction

The American Federation for Aging Research reports that calorie restriction has health benefits. Since an excessive calorie deficit causes calorie-restriction fatigue and, indeed, is a threat to life, any possible benefits are only manifested if the minimum daily caloric intake is consumed. In other words, calorie restriction offers wellness advantages if it's "undernutrition without malnutrition," says AFAR.

Preliminary research suggests calorie restriction slows some of the harmful effects that occur in cells and tissues in the aging process, notes AFAR. In some animals, studies show it may help protect the reproductive system, nervous system and hormone production from the ravages of aging.

A clinical trial published in Cell Metabolism in March 2018 explored the effects of calorie restrictions in human subjects. Although the study had only 53 participants, the results are worth noting because most of the earlier investigations on the topic involved animals.

The trial found that reducing calorie consumption by 15 percent for two years resulted in slowed aging and improved protection from some age-related diseases. Another discovery was that calorie restriction reduced systemic oxidative stress, which is associated with cancer, diabetes, Alzheimer's disease and Parkinson's disease. No adverse effects were noted from the 15 percent calorie reduction.