| Aspect | Hunger | Appetite |
|---|---|---|
| Definition | Hunger is the biological, physiological need for food to sustain energy and survival. | Appetite is the psychological desire to eat, often triggered by sensory cues rather than necessity. |
| Primary Driver | Hunger is driven by internal signals like empty stomach contractions and low blood glucose levels. | Appetite is driven by external factors such as food aroma, visual appeal, or social settings. |
| Core Mechanism | Hunger originates from the hypothalamus responding to hormonal signals like ghrelin and leptin. | Appetite originates from the brain's reward system, involving dopamine and sensory cortex activation. |
| Biological Basis | Hunger is a survival instinct regulated by the endocrine system to maintain energy homeostasis. | Appetite is a learned behavior influenced by memory, culture, and past eating experiences. |
| Onset Speed | Hunger develops gradually over hours, typically 3-5 hours after the last meal. | Appetite can appear instantly upon seeing or smelling food, even right after a full meal. |
| Time of Occurrence | Hunger follows a predictable pattern tied to meal timing and daily energy expenditure. | Appetite occurs sporadically, often triggered by environmental cues like commercials or buffets. |
| Feeling Location | Hunger is felt primarily in the stomach as gnawing, cramping, or rumbling sensations. | Appetite is felt in the mind and mouth, manifesting as a craving or thought about specific foods. |
| Intensity Level | Hunger escalates in intensity over time, becoming urgent and uncomfortable if unaddressed. | Appetite intensity fluctuates rapidly and can vanish just as quickly as it appears. |
| Specificity of Craving | Hunger is non-specific; almost any food will satisfy the biological need. | Appetite is highly specific, often targeting a particular taste like sweet, salty, or crunchy. |
| Satiety Response | Hunger is satisfied by any food that provides calories and nutrients to the body. | Appetite is satisfied only by the specific food craved, otherwise the desire persists. |
| Hormonal Control | Hunger is controlled by ghrelin (stimulates) and leptin (suppresses) from the digestive system. | Appetite is controlled by serotonin, neuropeptide Y, and endorphins in the central nervous system. |
| Evolutionary Purpose | Hunger evolved to prevent starvation by ensuring consistent energy intake for survival. | Appetite evolved to encourage consumption of varied, nutrient-dense foods when available. |
| Relationship to Stress | Hunger typically decreases during acute stress due to cortisol suppressing digestive signals. | Appetite often increases during chronic stress, driving emotional eating of high-calorie comfort foods. |
| Effect of Hydration | Hunger can be temporarily reduced by drinking water, which stretches the stomach wall. | Appetite is largely unaffected by water intake, as thirst and craving pathways are separate. |
| Impact of Sleep | Hunger increases with sleep deprivation due to elevated ghrelin and reduced leptin production. | Appetite for high-fat foods rises by roughly 20% after a single night of poor sleep. |
| Response to Exercise | Hunger increases after intense exercise as muscles deplete glycogen stores and require refueling. | Appetite often decreases immediately after exercise due to suppressed orexin and blood flow redistribution. |
| Influence of Age | Hunger signals weaken with age, leading to reduced food intake and risk of malnutrition in elderly. | Appetite changes across life stages, peaking during adolescence and declining in older adulthood. |
| Role of Medications | Hunger is suppressed by GLP-1 agonists like semaglutide, which slow gastric emptying. | Appetite is altered by antidepressants and antipsychotics, often causing significant weight gain. |
| Connection to Emotions | Hunger is not triggered by emotions; it persists regardless of mood state. | Appetite is strongly linked to mood, with boredom, sadness, and anxiety triggering food cravings. |
| Cultural Influence | Hunger is universal across all cultures, driven by biology rather than social norms. | Appetite is shaped by cultural food preferences, meal times, and traditional celebration dishes. |
| Measurement Method | Hunger is measured using visual analog scales rating stomach emptiness and physical discomfort. | Appetite is measured using food-specific craving questionnaires and palatability ratings. |
| Effect of Fiber Intake | Hunger is reduced by high-fiber meals, which slow digestion and prolong stomach fullness for hours. | Appetite remains active even after fiber-rich meals, as sensory desire is not fully suppressed. |
| Protein Influence | Hunger is strongly suppressed by protein intake, which increases PYY hormone and reduces ghrelin. | Appetite for sweets often persists after protein meals, as protein does not fully satisfy sensory cravings. |
| Blood Sugar Link | Hunger rises sharply when blood glucose drops below the normal fasting range of 70-99 mg/dL. | Appetite spikes when blood sugar fluctuates rapidly, particularly after consuming refined carbohydrates. |
| Persistence Duration | Hunger persists until caloric needs are met, sometimes lasting hours if food is unavailable. | Appetite typically fades within 10-20 minutes if the craved food is not consumed. |
| Weight Management Role | Hunger is the primary driver of necessary food intake, essential for maintaining baseline body weight. | Appetite is the primary driver of overeating, responsible for most excess calorie consumption. |
| Disorder Association | Hunger dysfunction is linked to conditions like Prader-Willi syndrome, causing insatiable hunger. | Appetite dysfunction is linked to binge eating disorder, where cravings occur without physical hunger. |
| Intervention Approach | Hunger is managed through meal timing, portion control, and choosing high-satiety foods. | Appetite is managed through behavioral strategies, mindful eating, and environmental cue removal. |
| Typical Daily Episodes | Hunger occurs in predictable waves, typically 2-4 distinct episodes per day aligned with meals. | Appetite can trigger 10-20 separate food thoughts daily, many unrelated to actual energy needs. |
| Best-Fit Scenario | Hunger is best addressed by eating balanced meals with protein, fiber, and healthy fats. | Appetite is best managed by identifying triggers, practicing portion control, and delaying gratification. |
Hunger is the biological signal that drives you to eat when your body requires energy. It emerges from hormonal and neural cues, primarily ghrelin, and exists to maintain stable blood glucose levels. Without hunger, you would not reliably consume the calories needed for survival.
Hunger is the physiological state triggered by an empty stomach and falling nutrient levels, which activates hypothalamic pathways to produce a compelling urge for food intake. This drive is distinct from appetite, which is the psychological desire for specific foods. Hunger is survival-based, whereas appetite is pleasure-based.
| Characteristic | What It Means in Practice |
|---|---|
| Biological trigger | Hormones like ghrelin rise when the stomach is empty, signaling the brain to initiate eating behavior. |
| Gradual onset | Hunger builds slowly over hours after digestion, unlike appetite which can appear suddenly with food cues. |
| Physical symptoms | Stomach growling, weakness, headache, or difficulty concentrating are common signs that energy stores are low. |
| Satiety response | Eating stops hunger within 20 minutes as stretch receptors and hormones like leptin signal fullness to the brain. |
| Non-specific food drive | Hunger makes almost any food appealing; you will eat a plain sandwich, not just a preferred snack. |
| Survival function | This mechanism ensures consistent calorie intake, protecting against malnutrition and metabolic slowdown. |
| Time-dependent | Hunger intensity increases with fasting duration, peaking around 6-8 hours after the last meal. |
| Emotional resilience | Hunger persists even during stress or boredom, whereas appetite often disappears under the same conditions. |
| Hormonal regulation | Ghrelin, insulin, and peptide YY work together to balance hunger signals against energy expenditure. |
| Universal experience | Every healthy human feels hunger daily; its absence can indicate metabolic disorders or chronic disease. |
| Advantages | Limitations |
|---|---|
| Ensures consistent energy intake to support basic metabolic functions and daily activity. | Chronic hunger can lead to overeating when access to high-calorie foods is unrestricted. |
| Signals nutrient deficiencies early, prompting you to consume a varied diet. | Hunger does not distinguish between needed nutrients, so you may crave empty calories. |
| Drives food-seeking behavior that has historically ensured human survival. | Intense hunger impairs cognitive performance, reducing focus, memory, and decision-making quality. |
| Regulates meal timing naturally, creating a predictable eating schedule. | Persistent hunger increases irritability and can strain personal relationships. |
| Helps maintain body weight by matching food intake to energy expenditure. | Hunger can override dietary intentions, leading to unplanned snacking or binge episodes. |
| Acts as a protective mechanism against starvation during food scarcity. | Hormonal hunger signals can misfire in obesity, causing false hunger despite adequate fat stores. |
| Promotes awareness of your body's energy state and metabolic health. | Ignoring hunger for long periods can trigger gallstones or metabolic adaptation. |
| Facilitates social bonding through shared meal times driven by mutual hunger. | Hunger amplifies stress hormones like cortisol, worsening anxiety in vulnerable individuals. |
| Enables weight management when paired with mindful eating practices. | Uncontrolled hunger can lead to rapid weight gain when high-calorie foods are always available. |
| Provides a clear biological cue to stop sedentary behavior and seek nourishment. | Extreme hunger from restrictive diets often causes rebound overeating and weight cycling. |
Appetite is the psychological desire to eat that drives food-seeking behavior based on learned cues, habits, and environmental triggers. It exists to motivate nutrient intake beyond mere survival, helping humans plan meals, enjoy social eating, and maintain energy balance through anticipation rather than urgent biological need.
Appetite is a conditioned psychological drive that stimulates food consumption through sensory input, memory, and social context, operating independently of immediate energy deficits. Unlike hunger's physiological urgency, appetite reflects hedonic reward pathways and cognitive associations that regulate eating patterns across daily routines and cultural practices.
| Characteristic | What It Means in Practice |
|---|---|
| Psychological origin | Appetite arises from brain reward circuits and learned associations, not from empty stomach signals or low blood glucose levels. |
| Sensory trigger | Sight, smell, and texture of food activate appetite even when the body has sufficient energy stores available. |
| Learned behavior | Childhood food experiences and cultural traditions shape individual appetite preferences that persist across a lifetime. |
| Context dependent | Time of day, social setting, and emotional state significantly influence whether appetite increases or decreases in any situation. |
| Hedonic component | Pleasure-seeking drives appetite toward highly palatable foods rich in sugar, fat, and salt rather than balanced nutrition. |
| Malleable response | Appetite can be trained through repeated exposure, portion awareness, and mindful eating practices to favor healthier choices. |
| Separate from hunger | Appetite can persist after a full meal, while hunger can exist without any desire to eat specific foods. |
| Hormonal influence | Ghrelin, leptin, and gut peptides modulate appetite intensity, but psychological factors often override these chemical signals. |
| Variability pattern | Appetite fluctuates daily and weekly based on stress, sleep quality, physical activity, and menstrual cycle phases. |
| Environmental sensitivity | Food advertising, portion sizes, and buffet displays amplify appetite through external cues that bypass internal regulation. |
| Advantages | Limitations |
|---|---|
| Encourages varied nutrient intake by making different foods appealing across different days and meal occasions. | Promotes overconsumption of hyper-palatable processed foods that bypass natural satiety signals and drive weight gain. |
| Supports social bonding through shared meals that strengthen family and community relationships across cultures. | Leads to emotional eating patterns that use food to manage stress, anxiety, or sadness rather than address root causes. |
| Motivates food preparation and cooking skills that preserve culinary traditions and dietary knowledge across generations. | Creates vulnerability to manipulative food marketing that exploits sensory triggers to increase purchase and consumption. |
| Helps maintain adequate energy intake during growth periods, pregnancy, and recovery from illness or injury. | Contributes to mindless eating behaviors that disconnect consumption from conscious awareness and portion control. |
| Enables flexible eating patterns that adapt to changing schedules, travel, and lifestyle demands without rigid rules. | Produces food cravings that interfere with weight management efforts and create guilt cycles around eating choices. |
| Enhances meal enjoyment and satisfaction through anticipation and sensory pleasure that improve overall quality of life. | Distorts perception of true hunger, making it difficult to recognize genuine physiological need versus psychological desire. |
| Facilitates introduction of new foods through repeated exposure, expanding dietary variety and nutritional adequacy. | Responds to environmental cues like large portions or buffet displays that override internal fullness signals. |
| Provides motivation for grocery shopping and meal planning that supports household food security and preparation. | Fluctuates with hormonal changes, causing unpredictable eating patterns that complicate consistent nutrition adherence. |
| Signals food quality and safety through sensory evaluation that guides appropriate food selection and rejection. | Can become dysregulated in eating disorders, leading to either extreme restriction or uncontrolled binge eating episodes. |
| Creates positive associations with nourishing foods that support long-term healthy eating habit formation. | Diminishes with age or medication use, reducing interest in food and potentially leading to unintended weight loss. |
| Shared Aspect | How Hunger and Appetite Are Alike |
|---|---|
| Biological Drive | Both hunger and appetite originate from complex brain-body signaling pathways that regulate energy intake and survival. |
| Hypothalamus Control | Hunger and appetite both rely on the hypothalamus to integrate hormonal, neural, and metabolic cues for eating behavior. |
| Hormonal Influence | Ghrelin and leptin modulate both hunger and appetite, though their relative impact differs between the two states. |
| Energy Regulation | Both hunger and appetite serve to maintain adequate energy balance, preventing caloric deficits or excesses. |
| Nutrient Seeking | Hunger and appetite both motivate the search for and consumption of macronutrients like carbohydrates, fats, and proteins. |
| Behavioral Output | Both hunger and appetite trigger food-seeking behaviors, including planning, foraging, and actual eating actions. |
| Neural Pathways | Hunger and appetite share overlapping neural circuits, including the arcuate nucleus and reward-related dopamine pathways. |
| Gut-Brain Axis | Both hunger and appetite are shaped by gut-derived signals, such as cholecystokinin and peptide YY, that communicate satiety. |
| Psychological Component | Hunger and appetite both involve cognitive processes like anticipation, memory of food, and learned preferences. |
| Environmental Triggers | Both hunger and appetite can be initiated by external cues, including food sights, smells, and social contexts. |
| Temporal Rhythms | Hunger and appetite both follow circadian patterns, peaking at predictable times across a 24-hour cycle. |
| Homeostatic Goal | Both hunger and appetite aim to restore or maintain internal homeostasis, though appetite may override it. |
| Evolutionary Function | Hunger and appetite both evolved to ensure adequate food intake for growth, reproduction, and physical activity. |
| Individual Variability | Both hunger and appetite vary significantly across individuals due to genetics, age, sex, and metabolic rate. |
| Measurement Methods | Hunger and appetite are both assessed using subjective rating scales, such as visual analog scales, in research settings. |
| Dietary Influence | Both hunger and appetite respond to meal composition, with high-protein or high-fiber foods reducing both more effectively. |
| Hydration Link | Hunger and appetite both increase when dehydrated, as thirst signals can be misinterpreted as food cravings. |
| Stress Response | Both hunger and appetite are amplified by cortisol and stress, leading to increased eating in many individuals. |
| Sleep Interaction | Hunger and appetite both rise with sleep deprivation, driven by altered ghrelin and leptin levels. |
| Medication Effects | Both hunger and appetite can be suppressed or stimulated by the same drugs, such as GLP-1 receptor agonists. |
| Clinical Assessment | Hunger and appetite are both evaluated in eating disorder diagnoses, though their specific patterns differ. |
| Age-Related Changes | Both hunger and appetite decline with aging, contributing to reduced food intake and risk of malnutrition in older adults. |
| Physical Activity Impact | Hunger and appetite both increase after moderate-to-vigorous exercise, though acute suppression can occur. |
| Palatability Effect | Both hunger and appetite are enhanced by highly palatable foods, which increase eating beyond metabolic need. |
| Learning and Conditioning | Hunger and appetite both are shaped by associative learning, linking specific foods with post-ingestive outcomes. |
| Sociocultural Norms | Both hunger and appetite are influenced by cultural eating patterns, portion sizes, and meal timing conventions. |
| Metabolic Feedback | Hunger and appetite both receive feedback from blood glucose levels, free fatty acids, and amino acid concentrations. |
| Long-Term Health | Both hunger and appetite dysregulation contribute to chronic conditions like obesity, diabetes, and cardiovascular disease. |
| Intervention Targets | Hunger and appetite both are targeted by behavioral, pharmacological, and surgical weight-management interventions. |
| Subjective Experience | Hunger and appetite both produce conscious sensations, though hunger is more visceral and appetite more cognitive. |
The single variable that decides it is biological need versus psychological desire. Choose based on whether your body truly requires fuel or your mind simply craves pleasure. This distinction prevents overeating and supports mindful eating.
Choose Hunger when your stomach is empty, you feel physical weakness, or it has been 4-5 hours since your last meal. Trust it during scheduled meals, after intense exercise, or when your blood sugar drops. Hunger signals a genuine caloric deficit.
Choose Appetite when you eat for pleasure, boredom, or social reasons, not physical need. Use it for special occasions, tasting new cuisines, or enjoying a dessert mindfully. Appetite works best when your stomach is already full but you seek sensory satisfaction.
| Common Myth | The Reality |
|---|---|
| "Hunger and appetite are the exact same physical sensation." | Hunger is the biological drive for fuel, while appetite is the psychological desire to eat, often triggered by cues like sight or smell. |
| "A rumbling stomach is the only reliable sign of true hunger." | Hunger also manifests as low energy, difficulty concentrating, or irritability, even without audible stomach noises. |
| "Appetite always disappears when you are truly physically hungry." | Appetite can remain high during hunger, but it can also persist after eating, driven by habits or emotions rather than energy needs. |
| "Eating a large meal instantly eliminates all hunger signals for hours." | Hunger suppression depends on meal composition; high-protein or high-fiber meals delay hunger longer than simple carbohydrates do. |
| "Feeling hungry means your body is running out of energy completely." | Hunger typically begins when blood glucose levels drop moderately, not when energy stores are depleted, acting as a preventive signal. |
| "Appetite is purely a mental construct with no biological basis." | Appetite involves hormones like ghrelin and neuropeptides, but it is heavily modulated by learned preferences and environmental context. |
| "Drinking water can completely replace the need for food when hungry." | Water can temporarily stretch the stomach to reduce hunger pangs, but it provides zero calories, so true hunger returns quickly. |
| "Boredom eating always stems from a lack of willpower, not appetite." | Boredom eating is a learned appetite response that increases dopamine, but it can be rewired with alternative sensory activities. |
| "Hunger is always a reliable indicator that you must eat immediately." | Hunger signals fluctuate naturally; mild hunger can be tolerated for short periods without harm, unlike severe hypoglycemia. |
| "Appetite is stronger in the morning for everyone after waking up." | Morning appetite varies widely; many people experience low ghrelin levels after waking, with appetite peaking later in the day. |
| "Spicy foods always reduce appetite and help you eat less overall." | Capsaicin can transiently reduce appetite in some people, but tolerance builds quickly, and effects on total intake are inconsistent. |
| "Stress always kills your appetite, making you eat less." | Acute stress often suppresses hunger via adrenaline, but chronic stress raises cortisol, which typically increases appetite for high-calorie foods. |
| "Chewing gum is a proven method to permanently reduce appetite." | Chewing gum may reduce snacking in the short term, but it can also trigger cephalic phase responses that increase hunger in some individuals. |
| "Hunger pangs are always located in the stomach region only." | Hunger can be perceived as a headache, weakness, or shakiness, which are systemic signs of glucose need, not just stomach contractions. |
| "Appetite is entirely separate from your body's nutritional requirements." | Appetite often tracks specific nutrient deficits, like craving salty foods after sweating, but it can be distorted by processed food formulations. |
| "Eating slower always reduces appetite more than eating quickly." | Eating slower helps some people feel fuller sooner, but total calorie intake and meal composition are stronger determinants of appetite control. |
| "Cold temperatures always increase your appetite and food intake." | Cold exposure can increase hunger in some contexts, but it also activates brown fat, which may suppress appetite through heat production. |
| "Appetite is the same thing as craving a specific food item." | Appetite is general desire to eat, while a craving is a specific urge for a particular food, often linked to memory or mood. |
| "If you are hungry, you must have low blood sugar levels." | Hunger can occur with normal blood glucose; it is often triggered by falling glucose levels or empty stomach volume, not absolute lows. |
| "Protein only helps build muscle; it does not affect appetite." | Protein is the most satiating macronutrient, reducing hunger hormones like ghrelin and increasing peptide YY, which lowers appetite. |
| "Appetite is fixed and cannot be changed over time." | Appetite is highly adaptable; repeated exposure to smaller portions or different foods can reset portion size expectations and hunger cues. |
| "Fiber supplements are as effective as whole foods for appetite control." | Whole foods with fiber provide bulk and viscosity that slow digestion more effectively than most isolated fiber supplements do. |
| "Hunger always disappears after you drink a sugary soda." | Sugary drinks spike glucose then cause a rapid drop, which can increase hunger shortly after, unlike solid foods that stay in the stomach. |
| "Visualizing food always increases your appetite and makes you eat more." | Imagining eating a specific food repeatedly can actually reduce appetite for that food through habituation, a technique called mental satiety. |
| "Appetite is only controlled by the brain, not the stomach." | The stomach sends stretch signals via the vagus nerve, and gut hormones like cholecystokinin inform the brain, making it a two-way system. |
| "A high-fat meal always keeps you full longer than a high-carb meal." | Fat slows gastric emptying, but protein and fiber often provide greater satiety per calorie than fat, which can be energy-dense and less filling. |
| "Skipping breakfast always makes you hungrier later in the day." | Some people experience lower appetite after skipping breakfast due to reduced ghrelin, while others overeat later; individual responses vary. |
| "Appetite is always high when you are dehydrated." | Dehydration can sometimes be mistaken for hunger, but it often suppresses appetite in older adults, leading to reduced food intake. |
| "Eating quickly is the only reason you overeat at meals." | Overeating results from a combination of large portions, low satiety foods, and distraction, not just eating speed alone. |
| "Hunger and appetite are completely independent of your sleep quality." | Sleep deprivation raises ghrelin and lowers leptin, which increases hunger and appetite, especially for high-carbohydrate, calorie-dense foods. |
Difference Between Hunger and Appetite comes down to biology versus psychology. Hunger is your body's physical need for fuel, while appetite is your learned desire to eat. Choose hunger when your stomach signals emptiness. Choose appetite only when you genuinely want pleasure, not just food.
## FAQ ### What is the basic difference between hunger and appetite? Hunger is the biological drive for survival triggered by physiological signals like an empty stomach and low blood glucose, while appetite is the psychological desire to eat based on sensory cues, habits, or emotions, often persisting even when the body has sufficient energy. ### Which is stronger for controlling food intake: hunger or appetite? Hunger is stronger for controlling food intake because it is driven by survival mechanisms involving hormones like ghrelin and the hypothalamus, whereas appetite is a learned or hedonic response that can be more easily overridden by conscious decisions, environmental changes, or behavioral strategies. ### Can you feel hungry without having an appetite? Yes, you can feel hungry without having an appetite, which commonly occurs during illness, intense stress, or as a side effect of certain medications, where the physical need for fuel exists but the brain suppresses the desire to eat due to nausea, anxiety, or altered taste perception. ### Is appetite the same as hunger in medical terms? No, appetite is not the same as hunger in medical terms; hunger is a physiological state of nutrient deficit requiring energy intake, whereas appetite is a psychological or sensory phenomenon that influences food choice and eating frequency, and they are regulated by distinct neural pathways and hormonal signals. ### What are the main hormonal drivers of hunger versus appetite? The main hormonal driver of hunger is ghrelin, which increases before meals and signals the hypothalamus, while appetite is primarily influenced by dopamine, serotonin, and endocannabinoids, which modulate reward, mood, and food palatability, with leptin acting as a long-term regulator that suppresses both hunger and excessive appetite. ### Which is better to manage for weight loss: hunger or appetite? Managing appetite is better for weight loss because hunger is a necessary biological signal that should not be ignored, whereas appetite is an optional desire that can be reduced through high-protein meals, adequate sleep, and mindful eating, allowing you to maintain a calorie deficit without fighting intense physical discomfort. ### Does eating a high-fiber meal reduce hunger more than appetite? Eating a high-fiber meal reduces hunger more than appetite because fiber increases stomach distension and slows gastric emptying, which prolongs the release of satiety hormones like peptide YY and cholecystokinin, but it does not directly suppress the hedonic desire for palatable foods triggered by external cues like advertising or social settings. ### What is a common beginner mistake when distinguishing hunger from appetite? A common beginner mistake is confusing boredom or stress-induced appetite with true hunger, leading to unnecessary snacking; to avoid this, use the "apple test" where you ask if you would eat a plain apple, and if not, the eating urge is likely appetite rather than physiological hunger. ### Can you switch from eating based on appetite to eating based on hunger? Yes, you can switch from eating based on appetite to eating based on hunger by practicing intuitive eating, which involves rating your hunger on a scale of 1 to 10 before meals, waiting 20 minutes after feeling full, and removing distracting stimuli like screens during meals to reconnect with internal satiety cues. ### How does stress affect hunger and appetite differently? Stress typically suppresses hunger by increasing cortisol and adrenaline, which inhibit digestive functions, but it often increases appetite for high-fat and high-sugar foods because those foods activate the brain's reward system to reduce anxiety, leading to stress-eating that is driven by emotional relief rather than energy need.