A cookbook editor's tour of the macros, micros, metabolism, and the diets you've been told to follow — with the evidence behind each, plainly stated.
All food breaks down into three macronutrients — carbohydrate, protein, fat — plus alcohol (a fourth caloric substrate), water, and the micronutrients (vitamins, minerals). Energy is measured in kilocalories: 1 kcal = 4.184 kJ.
| Macronutrient | kcal/g | Primary roles |
|---|---|---|
| Carbohydrate | 4 | Fast and stored fuel (glycogen) |
| Protein | 4 | Structure, enzymes, hormones |
| Fat | 9 | Dense fuel, membranes, hormones |
| Alcohol | 7 | None essential |
Sugars (simple) and starches/fibers (complex). Glucose is the brain's preferred fuel. Fiber — indigestible carbohydrate — feeds gut bacteria and lowers LDL cholesterol; aim for 25–38 g/day.
Made of 20 amino acids; nine are essential (must be eaten). RDA is 0.8 g/kg/day; active adults often benefit from 1.2–1.6 g/kg. Animal sources (eggs, dairy, meat, fish) and combined plant sources (legumes + grains) provide complete profiles.
Saturated, mono-unsaturated, poly-unsaturated. Essential fatty acids: omega-3 (ALA, EPA, DHA) and omega-6 (linoleic). Trans fats — industrially hydrogenated — are uniquely harmful and now banned in many countries.
A modern "MyPlate"-style guide (USDA, 2011, replacing the 1992 pyramid).
Vitamins are organic; minerals are inorganic. Both are required in milligrams or micrograms but their deficiency can be devastating: scurvy (C), beriberi (B1), pellagra (B3), rickets (D), goitre (iodine).
| Nutrient | Roles | Sources |
|---|---|---|
| Vitamin C | Collagen, antioxidant | Citrus, peppers, broccoli |
| Vitamin D | Calcium absorption, immunity | Sun, fatty fish, fortified milk |
| Vitamin B12 | Red cells, nerves | Animal foods, fortified cereal |
| Iron | Hemoglobin, oxygen carry | Red meat, lentils, spinach |
| Calcium | Bone, signaling | Dairy, leafy greens, tofu |
| Iodine | Thyroid hormone | Iodized salt, seafood |
| Magnesium | ~300 enzymes | Nuts, seeds, whole grains |
| Potassium | BP regulation, nerves | Bananas, beans, potatoes |
Total daily energy expenditure (TDEE) is the sum of:
Metabolism slows with age primarily because lean mass declines. Resistance training preserves it. Beyond modest individual variation, "slow metabolism" is rarely the cause of weight gain — but appetite regulation, sleep, and ultra-processed food formulation strongly are.
Olive oil, fish, legumes, vegetables, moderate wine. The PREDIMED trial (NEJM 2013) showed ~30% reduction in major cardiovascular events. Strongest overall evidence base of any named pattern.
Effective for short-term weight loss and for some seizure disorders (its original use, 1920s). Long-term cardiovascular safety depends on fat sources. Hard to sustain.
Dietary Approaches to Stop Hypertension. Lower sodium, high produce. Lowers BP comparably to a single antihypertensive medication.
Lower LDL, lower CV risk. Requires planning for B12, iron, omega-3, calcium, iodine.
16:8, 5:2, alternate-day. Comparable weight loss to caloric restriction; convenience matters more than any metabolic magic.
All animal foods. Anecdotal benefits; very little controlled evidence; concerns about fiber and long-term cardiovascular profile.
A Mediterranean spread — olive oil, vegetables, fish. Photo: Unsplash.
"Eat food. Not too much. Mostly plants." — Michael Pollan, In Defense of Food, 2008.
The NOVA classification (Monteiro et al., 2010) groups foods by processing level. Group 4 — ultra-processed — includes industrially formulated products with ingredients you would not find at home (high-fructose corn syrup, hydrolyzed proteins, emulsifiers).
Hall et al.'s 2019 metabolic-ward study (NIH) found that participants ate ~500 kcal/day more on an ultra-processed diet matched for macros and palatability. Reducing UPF intake is currently the single most evidence-supported dietary lever for weight and cardiometabolic health.
The first law of thermodynamics applies to bodies. To lose mass, energy out must exceed energy in. How the deficit is achieved — diet composition, frequency, time of day — affects sustainability and body composition far more than total efficacy.
A pound of body fat stores ~3,500 kcal; a sustainable deficit is 300–700 kcal/day. Aggressive deficits drive muscle loss, hunger, and rebound. Protein intake of 1.6 g/kg and resistance training preserve lean mass during weight loss.
Toss everything in a wide bowl. Per serving: ~520 kcal, 22 g protein, 60 g carbohydrate (12 g fiber), 22 g fat (mostly mono-unsaturated). Notable: 1.6 mg iron, 12 g protein from plants, full omega-9 profile from olive oil.
Nutrition is plagued by confounded observational studies, self-reported food frequency questionnaires, and short trial durations. A 12-week study cannot detect cancer or cardiovascular endpoints. Headlines change because effect sizes are small relative to noise. Trustworthy claims tend to be:
Layne Norton, PhD nutrition scientist, on protein, calories, and the realities of dieting research.
Books: How Not to Die, Greger · The Case Against Sugar, Taubes · Salt Sugar Fat, Moss · USDA Dietary Guidelines (free).
Nutritional needs vary by age, activity, pregnancy status, and disease. Talk to a registered dietitian or physician before changing diets in the context of medical conditions.