Athlete Energy Needs: Calculate How Much You Should Eat (Complete Practical Guide to TDEE and Energy Availability)

Opening: A Student Who Got Weaker the More She Trained

I’ve been coaching athletes for fifteen years, from junior high cross-country teams to amateur road cyclists and triathletes in Taiwan. Over the years, the most common mistake I’ve had to correct isn’t overtraining or pushing intensity too hard—it’s “not eating enough.”

A few years ago, a female student—let’s call her Xiao Ya—came to me feeling confused. She had increased her training volume from 150 km to 220 km per week, “controlled” her diet more strictly, and indeed lost two or three kilograms. But her power output on the bike didn’t go up—it went down. She got more and more winded on climbs, her menstrual cycle became irregular, and she pulled a muscle after an ordinary long ride. She thought the problem was her training plan. In reality, the problem was that her body had been in a chronic energy deficit, with nowhere near enough fuel to support the training she wanted to do.

When I sat down with her and calculated her true daily energy expenditure and actual intake, the answer was clear: she was running a deficit of roughly 500 to 700 kcal per day. That number doesn’t sound huge, but day after day, it adds up to a chronic physiological debt.

In this article, I want to lay out clearly—from concept to practice—how much athletes should eat. We’ll cover three things: the components of total daily energy expenditure (TDEE), how athletes can estimate their own TDEE, and a metric more important than body weight—Energy Availability (EA). This isn’t about turning you into a machine that weighs every bite of food and crunches numbers all day. It’s about helping you build a framework for “roughly knowing how much you should eat,” so your training can actually be supported by your body.

Here’s the bottom line: for the vast majority of serious recreational athletes, “eating too little” is more common—and more damaging—than “eating too much.”

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Conceptual Foundation: How Much Energy Does Your Body Actually Burn Each Day?

The Four Components of Total Daily Energy Expenditure (TDEE)

Many people assume that “burning calories” roughly equals “calories burned through exercise.” That’s the biggest misconception. In reality, your Total Daily Energy Expenditure (TDEE) is made up of four components, and exercise is often not the largest one.

According to the consensus in exercise physiology and sports nutrition, a typical person’s TDEE can be roughly broken down as follows:

Component	Description	Share of TDEE (typical range)	Characteristics
BMR (Basal Metabolic Rate)	Energy needed to sustain heartbeat, breathing, body temperature, organ function, and cellular repair while completely at rest	~60–70%	The largest component; highly correlated with fat-free mass
TEF (Thermic Effect of Food)	Energy expended to digest, absorb, and metabolize food itself	~10%	Highest for protein, moderate for carbohydrates, lowest for fat
EEE (Exercise Energy Expenditure)	Energy burned through deliberate exercise training	~5–15% (can be higher in athletes)	The component you can actively control
NEAT (Non-Exercise Activity Thermogenesis)	Walking, standing, housework, posture maintenance, even fidgeting	~15% (highly variable)	Often severely underestimated

Here are a few key concepts I always emphasize when working with athletes:

1. BMR is the big one: For most people, simply “being alive” accounts for 60–70% of daily energy expenditure. This is also why people with more fat-free mass (muscle) tend to have higher basal metabolic rates—muscle is an energy-hungry tissue.
2. Exercise burns less than you think: A solid two-hour group road ride might burn 1200–1600 kcal. That sounds like a lot, but spread across an entire day, it’s still just one part of TDEE. One bubble tea plus a serving of fried chicken can easily put it all back.
3. NEAT is the invisible variable: Two people of the same body weight—one sitting in an office all day, the other working as a delivery rider or in a job that requires constant movement—can differ by as much as 500–800 kcal per day from NEAT alone. This is why “applying the same formula to everyone” often doesn’t work.

Why “How Much to Eat” Can’t Be Determined by the Scale Alone

Many students ask me: “Coach, can’t I just adjust based on the scale? Eat less if I gain weight, eat more if I lose weight?”

The problem is that body weight is a delayed, noisy signal. Water, glycogen (each gram of glycogen carries about 3 grams of water), gut contents, and the female menstrual cycle can all cause body weight to fluctuate 1–2 kg within a single day. If you use a signal with that much noise to infer “how much I should eat today,” you’re very likely to make poor decisions—especially when you’re already under-eating and your body is quietly lowering its metabolic rate to protect itself.

This brings us to the real star of this article: Energy Availability (EA).

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Core Concept: Energy Availability (EA)

What Is EA, and Why Is It More Critical Than TDEE?

First, memorize this definition:

Energy Availability (EA) = (Daily Energy Intake − Exercise Energy Expenditure) ÷ Fat-Free Mass (kg)

In other words, EA is “after subtracting what exercise burns, how much energy your body actually has left to spend on sustaining life, repair, immunity, endocrine function, and bone health,” divided by your fat-free mass (FFM). The unit is “kcal / kg fat-free mass / day.”

It’s an elegant concept—and a brutal one. Because it tells you: if you burn a lot through exercise but don’t eat enough, even if your body weight looks fine, your body is essentially “borrowing” energy that should have gone toward maintaining health just to push through training.

EA Zones: From Ideal to Dangerous

According to the International Olympic Committee (IOC) consensus framework on Relative Energy Deficiency in Sport (REDs), EA can be roughly divided into several zones (treat the numbers as “general reference ranges”—individual variation is large):

EA Zone (kcal/kg FFM/day)	Status	What the Body Generally Experiences
≥ 45	Ideal	Relatively sufficient support for training, recovery, endocrine function, and bone health
~30–45	Suboptimal / Gray zone	Some physiological functions may begin to be affected; caution advised
< 30	Low Energy Availability (LEA)	Higher risk zone for endocrine, bone, and immune issues

This “30” threshold originates from laboratory studies conducted roughly twenty years ago on non-athletic women, which observed that menstrual and hormonal disruptions were more likely below this value. A special note: this number is not a sacred red line. Individual differences, sex, and circumstances all matter. If a corresponding threshold exists for men, it’s generally believed to be somewhat lower than for women. So in practice, I treat it as a warning light that tells you “it’s time to check whether you’re eating enough,” not a precise verdict.

(This threshold and the REDs concept reference the IOC’s 2023 REDs consensus statement and related literature; URLs are listed at the end of the article.)

Low Energy Availability (LEA) and REDs: It’s Not Just a Women’s Issue

In the past, this issue was framed as the “Female Athlete Triad” (low energy availability, menstrual dysfunction, and low bone density). However, recent consensus has expanded this into REDs (Relative Energy Deficiency in Sport), emphasizing that this is a problem that affects both men and women and impacts multiple systems throughout the body, including:

• Endocrine: Menstrual irregularities and amenorrhea in women; decreased testosterone and low libido in men.
• Skeletal: Decreased bone mineral density and increased risk of stress fractures—this is particularly common in runners.
• Immune: Frequent recurrent colds and slow wound healing.
• Metabolic: Lowered basal metabolic rate (the body’s “power-saving mode”), which makes it progressively harder to lose weight.
• Performance: Overall decline in strength, endurance, focus, and recovery speed—just like Xiao Ya from my opening example.

Looking back at Xiao Ya’s situation: her training volume spiked (increasing energy expenditure), while she deliberately ate less (decreasing energy intake). The numerator was squeezed from both ends, sending her EA directly into the danger zone below 30. She thought she was “trying harder,” but in reality, she was pushing her body into a long-term energy deficit.

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Practical Approach: Calculating Your TDEE and EA Step by Step

Alright, with the concepts covered, let’s get hands-on. I’ll walk you through a hypothetical but realistic case. All the numbers below are “reasonable estimates,” not precise measurements—please keep this premise in mind.

Step 1: Estimate BMR (Basal Metabolic Rate)

The most common method that doesn’t require equipment is the Mifflin-St Jeor equation (providing the standard estimation formula):

• Male: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
• Female: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

Case A: Xiao Ya, female, 30 years old, 163 cm, 55 kg.

BMR = 10×55 + 6.25×163 − 5×30 − 161 = 550 + 1018.75 − 150 − 161 ≈ 1258 kcal/day

Step 2: Multiply Daily Activity (Excluding Training) by an Activity Factor

This step estimates daily expenditure excluding formal training (BMR + TEF + NEAT). Common activity factors:

Lifestyle (excluding formal training)	Activity Factor	Applicable To
Sedentary (office work, minimal walking)	1.2–1.3	Office workers, students
Lightly active	1.4–1.5	Jobs involving frequent walking
Moderately active	1.6–1.7	Standing, manual labor jobs
Highly active	1.8–2.0	Physical labor, delivery, farm work

Xiao Ya is an office worker, so we use 1.3:

Daily expenditure (excluding training) ≈ 1258 × 1.3 ≈ 1635 kcal/day

Step 3: Add Exercise Energy Expenditure (EEE) for “Training Days” Separately

Here, I specifically recommend calculating training expenditure separately rather than lumping it all into one activity factor—you’ll understand why when we get to EA. Exercise expenditure can be estimated using a power meter, heart rate, or rough empirical values.

Rough reference (varies greatly by individual and intensity; for conceptual purposes only):

Activity	Approximate Expenditure (per hour)
Easy cycling / commuting	300–450 kcal
Moderate-intensity road group ride	500–750 kcal
High-intensity intervals / climbing workouts	700–1000+ kcal
Easy jogging	400–600 kcal
Swimming (moderate)	400–700 kcal

Quick tip: If you have a power meter, a practical rough estimate is “work done (kJ) ≈ expenditure (kcal),” because human cycling efficiency is about 20–25%, which numerically lands close to a 1:1 ratio. For example, a ride with 900 kJ of work can be treated as roughly 900 kcal of exercise expenditure.

Xiao Ya’s moderate group ride lasts about two hours, estimated at 1200 kcal.

Step 4: Calculate Training Day TDEE

Training day TDEE ≈ Daily expenditure 1635 + Training expenditure 1200 ≈ 2835 kcal/day

This means: On days Xiao Ya trains, just to maintain her weight, she needs to eat close to 2800 kcal. But when she “watches her diet,” she often only eats 1800–2000 kcal—a daily deficit of 800–1000 kcal. This is the root cause of her declining power output, irregular periods, and susceptibility to injury.

Step 5: Calculate EA to See If You’re Crossing the Line

First, estimate Fat-Free Mass (FFM). Assuming Xiao Ya’s body fat percentage is about 22%, then:

FFM = 55 × (1 − 0.22) ≈ 42.9 kg

Plugging in her intake of 1900 kcal during “dieting” and training expenditure of 1200 kcal into the EA formula:

EA = (1900 − 1200) ÷ 42.9 ≈ 700 ÷ 42.9 ≈ 16.3 kcal/kg FFM/day

16! This is far below the warning threshold of 30, and it’s no wonder her body is protesting.

If we raise her intake to 2700 kcal:

EA = (2700 − 1200) ÷ 42.9 ≈ 1500 ÷ 42.9 ≈ 35 kcal/kg FFM/day

This enters the suboptimal zone. If we push further to 2900 kcal, her EA would climb above 40, returning to a relatively safe range. This is the direction I eventually helped her adjust: keep training volume unchanged for now, and first focus on eating more.

Comparison Table of Two Cases

Let me add a male endurance-type Case B for comparison—it’ll give you a better feel:

Item	Case A (Xiao Ya / Female)	Case B (A-Zhe / Male)
Age / Height / Weight	30 / 163cm / 55kg	35 / 175cm / 70kg
Estimated BMR	≈ 1258 kcal	≈ 1649 kcal
Lifestyle Factor	1.3 (sedentary)	1.4 (frequent walking)
Daily Expenditure (excl. training)	≈ 1635 kcal	≈ 2309 kcal
Training Expenditure (that day)	≈ 1200 kcal	≈ 900 kcal (1 hr intervals)
Training Day TDEE	≈ 2835 kcal	≈ 3209 kcal
Fat-Free Mass (est.)	≈ 42.9 kg	≈ 58.1 kg (approx. 17% body fat)
EA if Intake = TDEE	≈ 38 (borderline adequate, depends on intake)	≈ 40 or so

The point isn’t to memorize these numbers, but to understand the process: first estimate expenditure, isolate training from it, then check whether EA is in the safe zone.

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Common Mistakes and Corrections

Over the years, I’ve seen too many smart, dedicated athletes fall into the same traps. Here are the most common ones, and how I fix them.

Mistake 1: Treating Exercise Expenditure as “Extra Calories You Can Skip Eating”

Many people think, “I rode for two hours and burned over a thousand calories, so I can eat less.” This is exactly what pulls both ends of the EA formula’s numerator down: exercise expenditure goes up, intake goes down, and EA collapses.

Correction: Training is an “expense,” not an “allowance.” The more you train, the more you need to eat, especially carbohydrates, to replenish glycogen stores and support the next workout and recovery.

Mistake 2: Only Caring About Protein, Ignoring Total Calories and Carbohydrates

Protein is certainly important (a common recommendation for endurance athletes is about 1.2–2.0 grams per kilogram of body weight, and possibly higher for strength-focused athletes), but if total calorie intake is insufficient, the protein you eat will be burned as fuel instead of being used to repair muscles. Recent REDs research has also specifically highlighted “low carbohydrate availability” as an independent issue.

Correction: First, make sure total calories and carbohydrates are sufficient; only then can protein fulfill its repair function. For endurance athletes, carbohydrates are the primary fuel and should not be demonized long-term.

Mistake 3: Treating “Sports Watch Calorie Burn Numbers” as Gospel

The calorie expenditure estimated by wearable devices often has significant errors, especially for activities that aren’t running or measured with a power meter. Some people go the other way and eat back all of the “3,500 calories burned today” shown on their watch, resulting in overeating.

Correction: Treat device numbers as a “trend reference,” not a precise ledger. For rides with a power meter, estimating from kJ is the most reliable; without one, just use the experiential ranges mentioned earlier to get a ballpark figure.

Mistake 4: Severely Under-eating on Rest Days “Because You Didn’t Train”

It’s true that you can eat a bit less on rest days (since training expenditure is lower), but many people overcorrect. Rest days are actually when the body is doing repair work and needs nutrition the most, yet they starve it.

Correction: On rest days, “fine-tune” rather than “slash.” Using Case A from earlier as an example, the rest day TDEE is about 1,635 kcal, which is over a thousand less than the 2,835 kcal on training days. Just scale down moderately; don’t drop below BMR.

Mistake 5: Treating “Being Thin” as the Only Goal, Ignoring Warning Signs

This is the most dangerous one. When athletes start showing these signs, I become very alert:

• Irregular or absent menstrual cycles in women
• Constantly feeling cold, cold hands and feet (a common sign of a down-regulated metabolism)
• Poor sleep, low mood, decreased libido
• Slow wound healing, frequent colds
• Stalled or declining training power/pace, slower recovery
• Recurring stress fractures or tendon issues

Correction: When several of the above appear, this isn’t a lack of willpower; it’s the body crying for help. What you should do is increase intake, reduce training load, and seek professional assistance.

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Taiwan-Specific Context: How Can People Who Eat Out Get Enough?

I know—when seeing “you need to eat 2,800 kcal a day,” many Taiwanese friends’ first reaction is: “I eat out for all three meals. How do I calculate that? How do I eat enough without eating junk?”

Here are practical tips I give to clients who eat out, using common Taiwanese foods:

Use “Portion Intuition” Instead of “Weighing Anxiety”

You don’t need to weigh every meal. Just use a few common Taiwanese reference points:

Common Taiwanese Food	Approximate Calories (portions vary by vendor)	Coach’s Notes
A bowl of white rice (about a fistful)	About 250–300 kcal	Good carbs after endurance training
An onigiri (rice ball)	About 180–250 kcal	Convenient fuel before/after training
A braised chicken leg bento box	About 700–900 kcal	Has both protein and carbs
A bowl of beef noodle soup	About 600–800 kcal	Replenishes fluids, sodium, and carbs; great in summer
A full-sugar bubble tea (700ml)	About 250–400 kcal	Fine for quick sugar replenishment after training; be careful otherwise
A serving of fried chicken cutlet	About 450–600 kcal	Fried; okay occasionally for calorie surplus
A banana	About 90–110 kcal	The most convenient fuel during training

Fueling Tips for Taiwan’s Climate

Taiwan’s summers are hot and humid. During long rides or road runs, you sweat a lot and lose electrolytes quickly. In these situations:

• Don’t just replenish water without sugar and sodium: For prolonged exercise, you need to take in carbs and electrolytes together, otherwise you risk hypoglycemia, cramping, or even heat exhaustion.
• Carbohydrate intake during exercise: For moderate-to-high intensity, long-duration efforts, aim for 30–60 grams per hour. For ultra-long events, you can go higher (individual tolerance varies greatly; you need to train your gut).
• Don’t just chug water when you get home: Prioritize a meal or snack containing both carbs and protein to make good use of the recovery window.

Making Good Use of Taiwan’s Healthcare and NHI System

If you’re already experiencing the warning signs mentioned earlier (menstrual irregularities, suspected stress fractures, chronic fatigue), Taiwan’s National Health Insurance makes it very convenient to see a doctor. Don’t just self-diagnose by looking up symptoms online:

• Suspected bone issues → Orthopedics / Sports Medicine clinic.
• Menstrual or hormonal issues → Obstetrics/Gynecology or Endocrinology.
• Need precise dietary planning → Seek out a registered dietitian (some hospitals have sports nutrition or weight management clinics).

These professional evaluations are far more reliable than crunching numbers yourself. The calculations in this article are just to help you establish a sense of direction; they cannot replace individualized clinical assessment.

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Actionable Advice for Readers of Different Levels

If You’re a Beginner “Just Starting Serious Training”

1. Don’t rush to lose weight. In the first few weeks of training, focus on “eating enough and being able to complete workouts.”
2. Use the formula above to calculate your training day TDEE once—you might be surprised at how much you actually need to eat.
3. Within 1–2 hours after training, remember to have a meal containing carbs + protein.
4. Observing body signals (sleep, energy, recovery) is more meaningful than weighing yourself daily.

If You’re an Advanced Athlete “Already Training Regularly, Looking to Break Through”

1. Calculate your EA separately from training expenditure and check if you’ve been chronically sitting below 30.
2. If you’re cutting fat, use a mild deficit (within 300–500 kcal per day) and ensure your EA doesn’t fall into the LEA zone.
3. Periodize your nutrition: Eat more carbs on high-intensity/long-distance days, fine-tune on rest days, rather than eating the same thing every day.
4. Periodically (e.g., every 4–6 weeks), review whether your weight trend, power/pace trend, and body signals are all consistent.

If You’re Already Experiencing Warning Signs (Menstrual Irregularities, Recurring Injuries, Declining Performance)

1. Assume you’re not eating enough and bring your intake back up—this is usually the most necessary and most overlooked step.
2. Proactively reduce training volume for a period to give your body a chance to repair.
3. Seek professional help: Sports Medicine / Orthopedics / OB-GYN / Endocrinology / Dietitian. Use your NHI resources to get a thorough check-up.
4. This isn’t weakness; it’s smart. Every athlete I’ve coached who was willing to step back and replenish their energy eventually rode farther and ran longer.

A Quick Self-Check Table: “Did I Eat Enough Today?”

Self-Check Question	Yes	No (Pay Attention)
Is recovery after training normal?	✅	⚠️ Possibly under-eating
Is sleep quality stable?	✅	⚠️
Are mood and focus normal?	✅	⚠️
Women: Is your menstrual cycle regular?	✅	⚠️ High alert
Do you often feel cold hands and feet?	⚠️	✅ (Not being cold is better)
Is your power/pace improving or maintained?	✅	⚠️
Do you have frequent colds or minor injuries?	⚠️	✅ (Not having them is better)

If several items fall into the “Pay Attention” column, don’t add more training to your plan—eat more first.

Advanced: Breaking Total Calories into Three Macronutrients

Calculating “how many calories to eat” is only the first step. In practice, I also help athletes break total calories into the three macronutrients—carbohydrates, protein, and fat—because for endurance athletes, having enough calories but not enough carbs will still cause problems (this is exactly what recent REDs research emphasizes about “low carbohydrate availability”).

Here are the rough allocation principles I commonly give endurance athletes (units are per kilogram of body weight; the ranges are for conceptual reference only and should be adjusted based on training load and goals):

Nutrient	General Training Day Recommendation (per kg body weight/day)	Calories per Gram	Coach’s Notes
Carbohydrates	About 5–8 g (can go up to 8–10+ on high-volume days)	4 kcal	Primary fuel; especially important before and after training—don’t stay low-carb long-term
Protein	About 1.4–2.0 g	4 kcal	Spread across multiple meals; about 20–40 g per meal is better absorbed
Fat	About 0.8–1.2 g	9 kcal	Needed for hormones and absorbing fat-soluble vitamins; don’t cut it too low

Let’s use Case A (Xiao Ya, 55 kg, training day TDEE ≈ 2835 kcal) as an example of how to allocate:

• Carbohydrates: Use 6 g/kg = 330 g → 330 × 4 = 1320 kcal
• Protein: Use 1.6 g/kg = 88 g → 88 × 4 = 352 kcal
• Fat: Use 1.0 g/kg = 55 g → 55 × 9 = 495 kcal
• Subtotal ≈ 2167 kcal, leaving about 668 kcal of room from 2835—can be filled with more carbs and fat (on heavy training days, usually more carbs).

You’ll notice that carbohydrates are the largest piece. This is why I keep reminding endurance athletes: don’t treat rice, noodles, or sweet potatoes as enemies—they are the fuel that lets you ride and run. Taiwanese food culture actually makes it very easy to get carbs; a bowl of rice, a serving of noodles, or a sweet potato are all great options.

Sample Daily Allocation (Training Day)

Spreading the numbers above across a day looks roughly like this (for demonstration only, not a prescription):

Time	Example Content	Key Point
Breakfast	Egg crepe + soy milk + one banana	Boot up with carbs and protein
1–2 hours before training	Rice ball or a slice of toast	Easily digestible carbs
During training (>90 min)	Banana/energy gel + electrolyte water	Replenish sugar and sodium while training
Within 1 hour after training	Bento box (rice + chicken leg + vegetables)	Carbs + protein to fill the recovery window
Dinner	Beef noodle soup or braised snacks + rice	Top off remaining daily calories
Before bed (optional)	A glass of milk or yogurt	Slow-release protein to aid repair

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Frequently Asked Questions (FAQ)

These are the questions I get asked most often after class and at talks—compiled here for you.

Q1: I want to lose fat—should I push EA down?

No. Fat loss comes from a “mild calorie deficit,” not from pushing EA into the danger zone. I usually recommend keeping the daily deficit within 300–500 kcal and making sure EA doesn’t stay below 30 long-term. The weight you lose by crushing EA is mostly water and muscle, and your metabolism will downshift—leaving you more stuck the more you cut. Losing slowly, staying able to train, and keeping normal body signals is what real fat loss looks like.

Q2: I don’t have a power meter—how do I estimate exercise expenditure?

Just pick a middle value from the “per-hour range” in the earlier table; you don’t need precision. For example, “2 hours of moderate-intensity riding” at 600 kcal per hour gives you 1200 kcal. Getting the direction right matters more than getting the decimal point right. Wearable device numbers can be a reference, but don’t treat them as gospel.

Q3: How much should I eat on rest days?

On rest days there’s no training expenditure, so TDEE is naturally lower—trim it moderately, but don’t drop below BMR. Using Xiao Ya as an example, about 1635 kcal on a rest day is a reasonable lower-bound reference. Rest days are actually key days for recovery, so protein and overall nutrition still need attention.

Q4: I’m a general exerciser purely aiming for weight loss—do I need to track EA too?

As long as you exercise regularly with some intensity, it’s worth using the EA concept to check whether you’re “eating too little and training too much.” Women, adolescents, and people who suddenly spike their training volume are high-risk groups for LEA, and should especially watch signals like menstrual cycles, sleep, mood, and recovery.

Q5: Are the numbers from these formulas accurate?

They’re all estimates, not measurements. The BMR formula, activity factors, and exercise expenditure each carry error at every step. The correct approach is: use the formula to get a starting point, then fine-tune over 2–4 weeks based on your body’s response (weight trend, performance, signals). Treat it as the starting coordinate for navigation, not a GPS for the destination.

Q6: I have a chronic condition (e.g., diabetes, high blood pressure)—can I follow this article?

Please consult your physician or dietitian first. The energy and nutrition needs of people with chronic conditions, as well as drug–exercise interactions, require individualized assessment and can’t be fitted into a general framework. This article provides general concepts, not a prescription for any disease.

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Conclusion: Treat Your Body as an Engine That Needs Fuel, Not an Opponent to Starve

Back to Xiao Ya’s story. What we did afterward was actually simple: keep training volume unchanged, increase daily intake—especially carbs—and get EA back above 40. After about six to eight weeks, her power came back, climbing felt less breathless, and her menstrual cycle gradually returned to normal. She told me: “I used to think I wasn’t training enough—turns out I wasn’t eating enough.”

I hope you remember that sentence too.

An athlete’s energy needs are not a subtraction problem of “the less, the better,” but a balance problem of “just right.” Your body is an engine that needs continuous fuel, not an opponent competing to see who can endure hunger longer. Once you calculate your total daily energy expenditure (TDEE) clearly and take care of energy availability (EA), training can truly be supported, and progress can happen.

Last but most important: all the formulas and numbers in this article are general estimation frameworks, and individual variation is huge. If you have a chronic disease (e.g., diabetes, high blood pressure, heart disease), are taking medication, or are already experiencing any of the health warning signs mentioned above, please defer to individualized professional assessment.

This article is educational content and cannot replace individualized diagnosis and treatment advice from a physician, physical therapist, or dietitian.

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References

• 2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs), PubMed: https://pubmed.ncbi.nlm.nih.gov/37752011/
• 2023 IOC consensus statement on REDs, Wu Tsai Human Performance Alliance: https://humanperformancealliance.org/news/2023-international-olympic-committee-consensus-statement-on-reds/
• Energy Availability and RED-S Risk Factors in Competitive, Non-elite Male Endurance Athletes, PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC8294781/
• Contributing Factors to Low Energy Availability in Female Athletes: A Narrative Review, PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC8912784/

Related Reading

• Calculating Caloric Intake for Runners: TDEE Calculation Methods for Different Training Volumes
• Special Nutritional Needs of Female Athletes: A Complete Coach’s Guide to Menstrual Cycles, Iron, Calcium, and Energy Availability
• Daily Management of Energy Availability for Female Endurance Athletes: Turning “Eating Enough” into an Executable Training Discipline
• Caloric Calculation During High-Intensity Training Periods: Balancing Energy Balance and Weight Management