An adult’s daily energy need is basal metabolic rate multiplied by a physical activity level, and for a 30-year-old 70 kg man of 175 cm that gives about 2,556 kcal at activity level 1.55 and 3,957 kcal at 2.4, while a 58 kg woman of 162 cm needs about 1,986 to 3,076 kcal over the same range. The caloric guide’s 3,500-4,500 kcal heavy-labour band matches a man, and for a woman it is out of reach.
Part of Caloric Budget for a Community
Adult energy requirement is the daily food energy that balances expenditure, estimated as basal metabolic rate times a physical activity level, with body size, sex, age and work all changing the result.
Every Per-Person Figure Needs Its Reference Person
A calorie figure with no body attached is not a requirement. This page names the person in every row: a 30-year-old man of 70 kg and 175 cm, and a 30-year-old woman of 58 kg and 162 cm. These reference bodies are illustrative choices of this page, not data on your community. Change them to match yours.
Sources And Method
Two published tools are used, both recalled and not read from this corpus.
- Mifflin-St Jeor equation (Mifflin and colleagues, American Journal of Clinical Nutrition, 1990): basal metabolic rate in kcal per day = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5 for men, or − 161 for women.
- Physical activity levels (PAL) from the FAO/WHO/UNU expert consultation on human energy requirements (report published 2004): sedentary or light-activity lifestyles 1.40-1.69; active or moderately active 1.70-1.99; vigorous 2.00-2.40. Total daily energy expenditure = BMR × PAL. Levels above 2.4 are not expected to be sustained over long periods.
Worked Example: Two Reference Adults
Man, 30 years, 70 kg, 175 cm:
- BMR = 10 × 70 + 6.25 × 175 − 5 × 30 + 5 = 700 + 1,093.75 − 150 + 5 = 1,648.75, about 1,649 kcal.
Woman, 30 years, 58 kg, 162 cm: 2. BMR = 10 × 58 + 6.25 × 162 − 5 × 30 − 161 = 580 + 1,012.5 − 150 − 161 = 1,281.5, about 1,282 kcal.
Multiply each by a PAL:
| PAL | Man (kcal/day) | Woman (kcal/day) |
|---|---|---|
| 1.55 (light) | 1,649 × 1.55 = 2,556 | 1,282 × 1.55 = 1,986 |
| 1.75 (moderate) | 2,885 | 2,243 |
| 2.0 (start of vigorous) | 3,298 | 2,563 |
| 2.2 | 3,627 | 2,819 |
| 2.4 (top of vigorous) | 3,957 | 3,076 |
A larger man changes the top row. At 90 kg and 185 cm: BMR = 900 + 1,156.25 − 150 + 5 = 1,911 kcal; × 2.2 = 4,205; × 2.4 = 4,587 kcal.
Reading The Caloric Guide Against These Numbers
The parent gives three adult bands: light labour 2,200-2,400, moderate 2,600-3,000 and heavy labour 3,500-4,500 kcal per day.
- The 2,600-3,000 band contains the man’s 2,885 at PAL 1.75 but lies above the woman’s 2,243 (PAL 1.75) and 2,563 (PAL 2.0).
- The 3,500-4,500 band is reached by the 70 kg man at PAL 2.2-2.4 (3,627-3,957) and by the 90 kg man (4,205-4,587). The 58 kg woman tops out at 3,076, so for a woman the heavy band is not reached at the top of the vigorous range.
- So the parent’s adult bands are best read as bands for an adult man of average to large build, mapping light to about 1.4-1.7, moderate to about 1.7-2.0 and heavy to about 2.0-2.4. That mapping is this page’s reading, not the parent’s statement.
The practical consequence is for allocation: a flat “adult” ration that gives a woman the heavy-labour figure over-feeds her, and one that gives a man the average under-feeds him.
How To Measure Your Own Community
Step 1: Weigh and measure the adults, or take representative samples by sex and work group. Step 2: Compute BMR for each group with the formula above. Step 3: Pick a PAL from the activity: the FAO bands above, assigned by hours of heavy work per day. Step 4: Check against body weight over time. As a rough rule recalled from nutrition science, about 7,700 kcal corresponds to 1 kg of body fat, so an adult eating 300 kcal a day too little loses roughly 300 × 30 ÷ 7,700 = 1.2 kg a month. Weight change also includes water and lean tissue, so use it as a trend, not a measurement. Step 5: Adjust rations when weights drift.
Common Mistakes
- Using one “adult” number. Men and women, small and large, differ by a thousand kcal.
- Applying PAL 2.4 all year. The heavy bands apply for the weeks of planting and harvest (Seasonal Labor Calorie Spikes).
- Trusting an equation for one person. It estimates a group’s average better than an individual; check against weight.
Safety
Chronic energy deficit in heavy workers
A worker whose intake stays below need loses weight, then strength, and becomes ill more easily. Watch for steady weight loss in the heavy-labour group and raise the ration before it shows in work output. This page gives no medical dosing; for children and pregnancy see Children, Pregnant, and Elderly Adjustments.
What’s Next
- Learn next: Children, Pregnant, and Elderly Adjustments — the people outside the adult table
- Combine with: Caloric Requirements by Population — turning person-level figures into a community total