So often, in both my personal and professional life,I hear folks say how fearful they are of calories, whether it’s about generally consuming “too many” or eating calorically dense foods deemed by diet culture to be “unhealthy.” As a dietitian, one of my missions is to help people understand how necessary and helpful calories are. After all, calories are energy, and we need a substantial amount of them (the exact amount varies from person to person) to stay alive and even more to thrive.

But our society has mostly lost sight of this reality, and tends to praise the idea of being in a calorie deficit as a good thing—when in fact, living in a negative energy balance is a serious problem. Today, we’ll delve into what it means to be in a negative energy balance, why it happens, the health risks of being in a calorie deficit, its role in eating disorders, and what to do instead when it comes to nutrition.

What is a negative energy balance?

A negative energy balance, also known as a calorie deficit, is when you consume fewer calories than you eat. This can occur for several different reasons, which we’ll go into below, but regardless of the reasons, it usually comes with a number of serious consequences for both mental and physical health, especially if it lasts for a significant period of time.

This might seem confusing, because in our society (especially on social media and in the diet and fitness industry) calorie deficits are generally viewed as a universally good thing, and something all of us should strive to achieve. So why is there this disconnect between how most people view calorie deficits, and how they actually impact you? The answer lies in our societal obsession with the pursuit of smallness. “Being in a negative energy balance is touted as a good thing in our society because we are taught from a young age that in order for someone to be ‘healthy,’ they have to be in a small body, even though research shows us that’s not the case,” explains dietitian Katie Schwartz, MS, RD, LD. “Since a negative energy balance may lead to initial weight loss, our society sees it as a sign of success, willpower and health,” adds dietitian Hilary Raciti, MS, RDN, CDN.

Why does a negative energy balance happen?

A negative energy balance happens anytime you don’t eat enough food to match your body’s energy needs. There are many reasons you might find yourself in this situation, so let’s explore some of the most common ways it happens:

Dieting for weight loss

Most restrictive diets aiming for weight loss cause an energy imbalance. In the U.S., around half of the population goes on a restrictive diet every year (thanks largely to diet culture). “The dieting industry is a multibillion-dollar industry that is constantly marketing towards people about how eating less calories is the answer to all of their problems,” Schwartz says. Keep in mind that diets typically don’t “work” in the long run, and they carry many negative consequences.

Unintentionally underfueling for sports or activity

Recent research highlights a high prevalence of undereating and energy deficits in certain groups, such as athletes experiencing low energy availability (a state where inadequate food intake combined with high energy expenditure leads to an imbalance). Such an imbalance can also happen when energy expended on physical labor or even the activities of daily living (also known as non-activity exercise thermogenesis) is higher than energy consumed.

Food scarcity

Living with food scarcity or food insecurity could cause someone to be in an energy deficit. In fact, data from the USDA shows that food insecure households in the U.S. typically consume fewer calories than food secure homes.

Eating disorders

Most of the time, eating disorders involve getting into a negative energy balance through disordered eating and exercise behaviors. “Though not always the case, many people with eating disorders find themselves in a chronic or temporary negative energy balance due to behaviors such as dietary restriction, self-induced vomiting, laxative use, or overexercise,” Raciti explains.

Digestive disorders

Research shows that people with inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, often experience energy deficits and malnutrition due to factors like low energy and nutrient intake, malabsorption, and increased energy expenditure.

Neurodivergence

There are several factors that put neurodivergent folks, such as those with autism spectrum disorder (ASD) or attention-deficit/hyperactivity disorder (ADHD), at risk for living in energy deficits. They may unintentionally skip meals due to factors such as medication side effects, hyperfocus (becoming completely absorbed in tasks), or reduced interoception (difficulty sensing hunger and fullness cues). Plus, they may experience decision fatigue—where mental overload makes food choices more difficult—and challenges with executive functioning skills, like planning meals.

Certain states requiring higher energy intake

There are several conditions that increase energy needs, like pregnancy and lactation, infections, or recovering from illnesses or injuries. If these increased energy needs aren’t met by eating more food, it will lead to a negative energy balance.

Some medical conditions and illnesses

Some medical issues, like hyperthyroidism, impact the metabolism, raising resting energy needs and making it more likely for a deficit to occur. Diseases impacting metabolism and appetite, like cancer, can also create a negative energy balance.

Some mental health issues

Anxiety can create a negative energy balance because of the increased energy expenditure caused by being in a fight-of-flight state. Other mental illnesses, like depression, can cause appetite loss or lack of motivation to eat or prepare food.

The relationship between eating disorders and negative energy balance

Most eating disorder diagnoses involve being in a negative energy balance at some point for some period of time. In fact, falling into a calorie deficit can sometimes be what triggers an eating disorder in the first place.

“Dropping into a negative energy balance can ignite eating disorders by causing a person's focus to shift to food and body image, and losing insight into other areas that are important to them,” says Equip lead dietitian Stephanie Kile, MS, RDN. In a 2023 study of patients with eating disorders found that calorie deficits were significantly associated with eating symptoms, anxiety, and body image concerns. Another 2024 study of teens and young adults found that engaging in any dieting in the last year was linked to greater eating disorder psychopathology—suggesting that the calorie deficits caused by dieting may contribute to the development or exacerbation of eating disorder symptoms.

Raciti adds that there are some physical and mental reasons why negative energy balance can ignite eating disorders. “[It] signals to the body that it’s unsafe. Remember, as humans we are designed for survival, not to become the smallest version of ourselves,” she explains. Her insight highlights one of the key takeaways of the landmark Minnesota Starvation Experiment: not eating enough food causes physical and psychological changes to a person, including becoming preoccupied with food (which is the body’s way of trying to survive). Raciti also says that the “body may drive strong urges to eat large amounts of food or even binge, often setting off a difficult cycle of restriction, bingeing, and compensatory behaviors.”

Additionally, being in a negative energy balance (whether unintentionally or intentionally) can put those in recovery from an eating disorder at risk for relapse. “For example, this could be due to the temptation of weight loss for an upcoming event, and they think they have control over it now—but losing weight and recovery are slippery slopes,” Kile explains. Raciti cautions that “even a few skipped meals or a seemingly small deficit can act as a spark that reignites disordered thoughts and behaviors in someone who is vulnerable or has a history of an eating disorder.”

How living in a negative energy balance impacts your health

Even if it doesn’t lead to an eating disorder, living in a calorie deficit can negatively impact your physical, emotional and mental health, both immediately and in the long-term. “Even a moderate deficit over time can impact nearly every system of the body, and if you don’t give your body what it needs, it will still find a way to survive — but in the least efficient, least supportive way possible,” Raciti explains. “It’s like running a factory without enough power: the machines keep going, but more slowly, less effectively, and at higher cost to the system.”

Here are a few of the many ways that living in a negative energy balance can impact you:

Mental and emotional issues

As mentioned above, the famous Minnesota Starvation Experiment found that negative energy balances can cause food preoccupation, increased anxiety, emotional dysregulation, feeling out of control around food, and even social isolation. “Your body’s only job is to keep you alive, and it does not know the difference between a diet and a famine,” Schwartz says. “Regardless of your weight or body size, when a basic biological need like food is not met, the autonomic nervous system shifts into a state of stress and threat, which only intensifies the cycle of preoccupation and dysregulation.”

Additionally, a negative energy balance can cause nutrient deficiencies over time, and being deficient in nutrients like vitaminB12, folate, and zinc is linked to depression, irritability, and cognitive issues. In fact, a 2021 meta-analysis shows that anorexia (which is characterized, in part, by being in a calorie deficit) is associated with cognitive decline, including memory impairment. Given the toll it takes on your mental and emotional well-being, it’s difficult to live a full, authentic life that’s in alignment with your values if you’re living in a negative energy balance.

Physical side effects

In the long run, living in a negative energy balance can cause serious health conditions like anemia and osteoporosis. The immune system can also weaken, since calorie deficits can lead to nutrient deficiencies in key immune-regulating nutrients, such as protein, fat, vitamins A, C, and D, and minerals like zinc and selenium. “Reproductive health is affected too, with loss of menstrual cycles, infertility, and poor libido being common,” Schwartz says. In fact, living in a negative energy balance is one factor that can contribute to hypothalamic amenorrhea, or the loss of a period for more than three months, according to The Journal of Clinical Endocrinology & Metabolism.

Being in a negative energy balance can eventually lead to a suppressed metabolism, which can cause many issues, including fatigue and cold intolerance. Plus, research shows that malnutrition and weight loss from being in a calorie deficit can slow the gastrointestinal (GI) tract, leading to conditions like gastroparesis (slowed movement of stomach muscles), reflux, bloating, constipation, and diarrhea—all which can impact quality of life significantly.

Living in a calorie deficit can also have life-threatening impacts on vital organs. “Prolonged deficits also place strain on the kidneys due to dehydration, electrolyte imbalances, and muscle catabolism, or breaking down muscle mass for energy,” Schwartz explains. “Over time, electrolyte imbalances can develop and, in severe cases, lead to sudden death.”

Increased eating disorder risk

As mentioned above, one major risk of calorie deficits is that they can contribute to eating disorder development or relapse. In those who are predisposed to eating disorders, being in a negative energy balance can be the triggering event that sets disordered thoughts and behaviors in motion. For those in recovery, eating under your body’s energy needs can shift the brain into a state where old thought and behavior patterns reemerge, and the eating disorder begins to regain control.

Healthy alternatives to a negative energy balance

Despite what diet culture says, there are ways to set nutrition goals and intentions that have nothing to do with living in a calorie deficit. “Your body doesn’t need to fall into a negative energy balance to see positive shifts in it, and fueling yourself properly will have more positive outcomes,” Kile says. Here are some ways to foster sustainable, life-supporting, and truly healthy food habits:

Focus on variety and balance

“Some great ways to pursue ‘healthy eating’ or more balanced eating is by making sure you consume a variety of foods, striving to have foods from all food groups within your day, eating from the rainbow of nutrients, and properly hydrating with water,” Kile encourages.

A good rule of thumb to use at meals is to include carbs like rice and bread, fats like butter and avocado, and proteins like beef and beans, plus fruits and veggies. I always recommend shooting for a relative balance, instead of a perfect one—for instance, if you don’t have veggies at lunch, don’t sweat it and see if you can have some late. And remember that eating fun foods —or as diet culture calls them, “junk food”—is part of having a balanced intake. A balanced diet can certainly include French fries and cake.

Shoot for consistency

Eating at regular intervals throughout the day will keep you feeling energized, focused, and more emotionally regulated (along with many other benefits). “Aim to have three meals a day and snacks as needed,” Kile suggests. While everyone has different needs, it’s best not to go longer than four or five hours without food during the day. “Our bodies thrive on consistent and frequent nutrient intake to support blood sugar levels, digestion, and overall regulation, and prevent intense hunger and cravings,” Schwartz adds.

Remember, not every day will be the exact same: some days you’ll be hungrier or simply require more fuel for your day’s activities than others. However, if you’re recovering from an eating disorder, following the same meal plan or eating pattern (ideally guided by a dietitian) for a significant period is often necessary.

Think about adding, not subtracting

Diet culture conditions us to focus on what we should take away from our plates, but what if you thought more about what you could add? “Instead, the question becomes, ‘What can I add to support my body?’” Schwartz says. “For example, if you feel like you’re not eating enough vegetables, you don’t need to stop eating burgers—you can simply add a side salad to your burger meal.” If you feel like you're lacking other nutritious foods (e.g. fruits or whole grains) on a regular basis, try adding at least one to each meal, instead of taking other foods away.

Instead of cutting carbs, Raciti suggests assessing whether any meals are lacking any of the macronutrients (carbs, fats, and proteins) that your body and brain need to function optimally instead. “If so, work on filling in that gap,” she recommends. Perhaps you’re missing carbs at breakfast, so you add toast or oats, or protein is lacking at lunch, so you add beans or turkey. If you think you generally may not be eating enough food and need to add to your overall intake, check out our article on how to fuel your body adequately.

Tune into your body

“Most of us are born with the ability to self-regulate energy intake,” Schwartz explains. However, both eating disorders and diet culture create a disconnection between the mind and the body, which makes it difficult or impossible to listen to and honor our body’s cues when it comes to food, movement, rest, and other needs. Fortunately, there’s a way to eat and care for your body that fosters healing and reconnection, called intuitive eating. Intuitive eating is a framework designed to support a healthier relationship with food that focuses on letting go of external rules and reconnecting with internal cues to guide eating and self-care habits.

Good places to start include taking stock of any food rules dictating your decisions, using a hunger fullness chart to notice what different levels of hunger and fullness feel like in your body, and noting how different food combinations and meals make you feel. For example, you might feel more energized when you have two carb sources at lunch instead of one, or perhaps you realize you’re more satisfied when you add avocado to your turkey sandwich.

Work with a dietitian

Dietitians are trained to help you reconnect with your body’s cues and find the best eating pattern to support your mental and physical well-being. Whether you want to learn to eat intuitively, understand your body’s nutrition and energy needs, or heal your relationship with food (or all of the above), having the support and guidance of a dietitian can be invaluable. When looking for a dietitian, make sure they take a non-diet approach to nutrition and that they’re experienced and trained in eating disorders if you’re struggling with one.

The truth is, living in a negative energy balance will keep you from living a healthy, full life and can bring serious and sometimes even life-threatening consequences. By focusing on other, life-supportive ways of eating and caring for your body while living in energy equilibrium, your body and brain will have what they need to support an authentic, dynamic, and healthy existence.