From calories to muscle science — everything you need to know, explained simply.
Nutrition is the science of how food provides your body with energy and the building blocks it needs to function, grow, and repair. Every food you eat contains a mix of nutrients — and the balance matters.
Calories are units of energy. Your body burns calories 24/7 — even while sleeping. Too few and you lose weight; too many and you gain. This is energy balance.
Thermic Effect of Food (TEF): Digesting food itself burns calories — protein burns ~25–30% of its own calories just to digest, while carbs burn ~5–10% and fats only ~0–3%.
Caloric density vs nutrient density: 100 kcal of dal gives you protein, fiber, iron, and B vitamins. 100 kcal of a biscuit gives you almost nothing but sugar and refined starch. Same calories, very different nutrition.
Every food is made of macronutrients — protein, carbohydrates, and fats. Your body needs all three in the right amounts.
Builds and repairs muscle, makes enzymes and hormones, supports immune function. The most filling macronutrient.
Complete vs incomplete proteins: Animal sources (eggs, chicken, dairy) contain all 9 essential amino acids. Plant sources (dal, rice, nuts) are incomplete — combine them to get complete protein.
Indian sources ranked (g protein per 100g): Chicken breast ~31g · Paneer ~18g · Eggs ~13g · Chana ~19g · Groundnuts ~26g · Dal ~9g cooked.
Glycemic impact: Protein has minimal effect on blood sugar, making it ideal for fat loss and sustained energy.
Your body's primary and preferred fuel source, especially for the brain and high-intensity exercise.
Simple vs complex: Simple carbs (sugar, white rice) digest fast — quick energy spike. Complex carbs (oats, brown rice, dals) digest slowly — sustained energy.
Glycemic Index (GI): Measures how fast a food raises blood sugar. Low GI (lentils, oats) is better for fat loss and sustained energy. High GI (white bread, sweets) causes spikes and crashes.
Stored as glycogen: Muscles and liver store carbs as glycogen — your body's first fuel reserve for workouts.
Essential for hormone production, vitamin absorption (A, D, E, K), brain health, and cell membranes.
Saturated fats (ghee, coconut oil, butter) — okay in moderation. Once vilified, now understood as neutral in reasonable amounts.
Unsaturated fats (groundnut oil, mustard oil, avocado, nuts) — actively beneficial. Omega-3s (fish, flaxseed) are anti-inflammatory.
Trans fats to avoid: Found in vanaspati, margarine, and commercial fried foods. Raise bad cholesterol (LDL) and lower good cholesterol (HDL).
Your body needs tiny amounts of these — but without them, everything breaks down. Most Indians are deficient in at least one.
Carries oxygen in blood. Deficiency causes fatigue, poor focus, weak immunity. Women especially at risk.
Feeds gut bacteria, slows digestion, stabilizes blood sugar. Most Indians eat far less than the 25–30g daily target.
Fat-soluble (A, D, E, K) store in body — excess can be toxic. Water-soluble (B, C) flush out daily and must be replenished.
Calcium builds bones, magnesium regulates 300+ enzymes, zinc boosts immunity. Anti-nutrients (phytates, oxalates) in plant foods reduce absorption.
Soluble vs insoluble fiber: Soluble fiber (oats, apple, dal) dissolves in water, lowers cholesterol, slows glucose absorption. Insoluble fiber (wheat bran, vegetables) adds bulk and prevents constipation.
Anti-nutrients in plant foods: Phytates in grains and legumes bind to iron, zinc, and calcium — reducing absorption. Oxalates in spinach bind calcium. Solution: soak dals before cooking, pair with Vitamin C, eat fermented foods.
Fat-soluble vitamin storage: Vitamins A, D, E, K are stored in fat tissue and liver. This means they can build up — excess Vitamin A or D from supplements can be harmful. Get them from food when possible.
Water powers digestion, nutrient transport, temperature regulation, and every chemical reaction in your body. Even 2% dehydration impairs physical and mental performance.
How much to drink: A simple formula — drink ~35ml per kg of body weight daily. A 70kg person needs ~2.5L. Add 500ml for every hour of exercise. In Indian summers, increase by 0.5–1L.
Signs of dehydration: Dark yellow urine, headache, low energy, dry mouth, muscle cramps. Your thirst sense lags behind actual dehydration — don't wait until you're thirsty.
Electrolytes matter: Sodium, potassium, and magnesium are lost through sweat. During intense exercise or hot weather, plain water isn't enough. Nariyal pani (coconut water), nimbu pani with salt, or buttermilk are excellent natural electrolyte sources.
Protein is made of amino acids — your body uses them to build muscle, make hormones, repair tissue, and run nearly every biological process.
9 essential amino acids: Your body cannot make these — you must eat them. They are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine.
PDCAAS score: Protein Digestibility Corrected Amino Acid Score rates protein quality from 0–1. Eggs = 1.0, whey = 1.0, beef = 0.92, soy = 0.91, kidney beans = 0.68, wheat = 0.42.
Dal + rice = complete protein: Dal is low in methionine; rice is low in lysine. Together they form a complete amino acid profile — one reason this combo has fueled Indian populations for centuries.
Anabolic window myth: You do NOT need to eat protein within 30 minutes of training. The window is 4–6 hours. Focus on total daily protein first — timing is a secondary concern.
Budget sources ranked (g protein per ₹10): Eggs (~5g) · Groundnuts (~4g) · Chana (~4g) · Dal (~3g) · Paneer (~2g) · Chicken (~2.5g). Eggs are the best value protein in India.
BMR (Basal Metabolic Rate) is the energy your body burns at rest — just to keep you alive. TDEE (Total Daily Energy Expenditure) is your full daily burn including activity.
Mifflin-St Jeor BMR (used in FitKharcha):
Men: 10×weight(kg) + 6.25×height(cm) − 5×age + 5
Women: 10×weight(kg) + 6.25×height(cm) − 5×age − 161
Activity multipliers for TDEE: Sedentary (desk job) ×1.2 · Light activity ×1.375 · Moderate (3–4 workouts/week) ×1.55 · Very active (daily training) ×1.725.
Why crash diets fail: Eating too little triggers metabolic adaptation — your body lowers BMR to survive. You also lose muscle, which further reduces metabolism. The deficit becomes unsustainable.
Metabolism and age: Metabolism slows ~2–3% per decade after 30, mostly because people lose muscle. Strength training preserves and builds muscle mass — the single best tool to keep metabolism healthy as you age.
Muscles grow when you challenge them with progressive overload, feed them enough protein, and give them time to recover. Miss any of the three and growth stalls.
Muscle Protein Synthesis (MPS): Resistance training causes micro-tears in muscle fibers. During recovery, your body repairs them larger and stronger — this is MPS. Protein provides the raw material for this process.
Progressive overload: Muscles only grow if the stimulus increases over time — more weight, more reps, shorter rest, or harder variations. Doing the same workout forever yields no growth.
Recovery window: Muscle repair takes 24–48 hours after training. Training the same muscle group daily is counterproductive — it prevents full repair. Rest is when you actually grow.
Sleep is when you grow: ~80% of growth hormone is released during deep sleep. 7–9 hours of quality sleep is not optional for muscle gain — it is when the building happens.
Fat loss happens in a sustained caloric deficit — your body turns to stored fat for energy when it can't get enough from food. There is no shortcut to this process.
Fat oxidation: In a deficit, the body breaks down triglycerides from fat cells into fatty acids and glycerol, then burns them for ATP (energy). This process requires a consistent deficit over weeks and months — not days.
Why the scale lies: Body weight fluctuates 1–3 kg daily based on water retention, glycogen, and gut contents. You can lose fat while the scale goes up. Measure trends over 2–4 weeks, not single days.
Preserve muscle while cutting: Eat adequate protein (1.8–2.2g/kg) and keep resistance training. Without these, up to 40% of weight lost in a deficit can be muscle — not fat. This worsens your body composition.
Very low calorie diets backfire: Eating below ~1200 kcal (women) or ~1500 kcal (men) triggers muscle loss, metabolic slowdown, hormonal disruption, and intense hunger — making the diet impossible to sustain.
When you eat matters far less than what and how much — but smart timing can optimize performance, recovery, and energy levels throughout the day.
Pre-workout: Eat carbs + protein 1–2 hours before training. Carbs provide energy; protein prevents muscle breakdown during the session. A banana + a glass of milk is simple and effective.
Post-workout window: You have 4–6 hours (not 30 minutes) to get protein for muscle repair. Don't rush — focus on total daily protein instead of stressing about the exact post-workout timing.
Breakfast myth: Skipping breakfast is fine — as long as you meet your total daily calorie and protein targets. Intermittent fasting works precisely because people skip breakfast without compensating later.
6 meals/day myth busted: Eating frequency has minimal effect on metabolism. 2 meals or 6 meals with the same total calories produce similar fat loss results. Eat in a pattern that fits your lifestyle.
Trillions of bacteria in your gut affect digestion, immunity, mood, and how efficiently you absorb nutrients. Indian cuisine has natural advantages here.
Prebiotics (fiber feeds good bacteria): Eat a variety of high-fiber foods — dals, vegetables, fruits, oats. Diversity in plant foods = diversity in gut microbiome = better health.
Fermented Indian foods as probiotics: Curd (dahi), idli and dosa batter, kanji, lassi, and buttermilk all contain live cultures that support gut health. Eat them regularly — they are genuinely functional foods.
Antibiotics and gut recovery: A course of antibiotics can wipe out large portions of gut flora. Rebuild by eating fermented foods and high-fiber plant foods for several weeks after finishing the course.
Gut-brain axis: Your gut produces ~90% of your body's serotonin. Poor gut health is linked to brain fog, anxiety, and low mood. A healthy gut is not just digestive — it affects mental clarity and emotional resilience.
No single diet is best for everyone. Here are the most common approaches — their strengths and how well they fit Indian food culture.
The fitness industry profits from confusion. Here's the science.
Your geography, diet culture, and genetics create specific nutritional considerations that most global advice misses.
Vegetarians get almost zero B12 from food. B12 deficiency causes irreversible nerve damage over time — fatigue, tingling in hands/feet, brain fog. Supplement 500–1000mcg daily or eat B12-fortified foods. Don't wait for symptoms.
India is sunny — yet 70%+ of the population is Vitamin D deficient. Darker skin requires more sun exposure to synthesize D3. Indoor lifestyles and clothes reduce skin exposure further. Supplement 1000–2000 IU daily, or 60,000 IU weekly (prescription dose).
Women are especially at risk. Plant iron (non-heme) absorbs at ~5–10% vs animal iron at ~25%. Strategy: pair iron-rich foods (palak, rajma, chana) with Vitamin C sources (nimbu, amla, tomato) to triple absorption. Avoid chai/coffee within 1 hour of iron-rich meals.
Dal + rice = complete protein (complementary amino acids). Combine multiple plant proteins daily. Add dairy (paneer, dahi, milk) to boost quality and quantity. If lacto-ovo vegetarian, eggs are the most efficient protein source available to you.
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Good information is out there — but so is a lot of noise. Here's where to find the real science.
Look for books by registered dietitians and sports nutritionists who cite peer-reviewed research. Topics to explore: sports nutrition, metabolic science, plant-based eating. Avoid books that make dramatic promises or sell branded supplements.
Seek science-based fitness channels where creators hold relevant credentials (RD, PhD in nutrition/exercise science) and cite studies in their content. Avoid channels that sell supplements or promote extreme diets. Good creators show you the research, not just conclusions.
ICMR (Indian Council of Medical Research) publishes India-specific dietary guidelines. WHO provides global nutrition fact sheets. PubMed for primary research. Prioritize systematic reviews and meta-analyses over individual studies — they aggregate evidence more reliably.
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