How Much Do you REALLY need to Eat?
Basic Terminology
1/ BMR (Basal metabolic rate): This is a term which refers to the minimum level of energy required to sustain your basic body functions such as breathing, digestion and circulation.
2/ NEAT (Non-Exercise Associated Thermogenesis): The energy requirements added by activities of day to day life. Things such as walking, talking, shopping, working, sitting, brushing your teeth, and even laughing. This also includes what people term INCIDENTAL EXERCISE, and is one of the most variable factors involving calorie requirements in a person. It has both 'innate' (unconscious) and 'learnt' (conscious) components. This means that although some people are more likely to 'move more' than others (that is - it is what keeps 'constitutionally lean' people LEAN - they simply fidget and move more than others), it is also something that everyone has a good amount of control over!
3/ EAT (Exercise Associated Thermogenesis): This is the energy requirements that are added to your requirements through planned exercise. Many people overestimate the requirements associated with this. The truth of the matter is that unless someone is doing large amounts of training it will not impact your requirements as much as you think!
4/ TEF (Thermogenic effect of feeding): The energy requirements associated with eating. It varies according to MACRONUTRIENT content of the foods (that is - if the food is a carbohydrate, a fat, or a protein) and also depends on factors such as the fibre content. It is a expressed as a percentage (%) lost of the TOTAL CALORIES CONSUMED. Protein has a higher energy cost when you eat it, and up to 25% of the energy ingested is 'lost'. Carbohydrates are variable, but usually fall between 5-25%, while fats has a low cost associated with digestion and utilisation, usually costing less than 5%. This means that the more protein & carbohydrates a person eats, the HIGHER the energy lost from their diet will be. If they eat a fat rich diet, the loss associated will be LOWER. For most mixed diets, it is something around 15%. REGARDLESS of what you have been told - this is NOT something that is dependent on MEAL FREQUENCY (15% of three meals containing 600 calories per meal, is the same as 15% of six meals containing 300 calories per meal).
5/ TEE (Total Energy Expenditure): This is your total daily energy requirement and is the sum of the above (BMR + NEAT + EAT + TEF).
As you can see by the above, there is therefore a multitude of things that impact a persons daily energy requirements.
- Age and Gender (males generally need more females for any given age)
- Total weight and lean mass (more weight and, specifically, a greater non fat mass means you need more energy)
- Physiological status (e.g.: sick or injured, pregnant, growing)
- Hormones (e.g.: thyroid hormone levels, growth hormone levels)
- Daily activity level (more activity = more needed)
- Exercise level (more activity = more needed)
- Diet (that is - your macronutrient intake)
So how do you know what to eat?
In order to calculate your energy requirements the most accurate measure would be via Calorimetry. This is the measure of the 'chemical reactions' in your body and the heat produced by these reactions. It can be measured directly (via placing you into a calorimeter where the heat you produce is measured) or indirectly (for example - placing you in a container and monitoring how much oxygen you use/ carbon dioxide and nitrogen you excrete over a given time). Although accurate - this is completely impractical for most people. So instead? We mostly rely on pre-set formula to try to calculate our needs.
Estimating Requirements
The simplest method of estimating needs is to quickly calculate your estimated requirements on standard 'calories per unit of weight (usually kilograms)'. An example of this would be:
- 25 to 30 kcals/kg/day for normal, healthy individuals with sedentary lifestyles doing little physical activity [11.5-13.5 kcal/pound]
- 30 to 35 kcal/kg/day for those involved in light to moderate activity 3-5 x a week with moderately active lifestyles [13.5-16 kcal/ pound]
- 35 to 40 kcals/kg/day for those involved in vigorous activity and highly active jobs [16-18 kcal/ pound].
These formula are very crude, and include ALL of the above variables in order to give you a basic starting figure for TOTAL daily energy needs.
There are then a number of more complex formula which firstly calculate your Basal Metabolic Rate, which then require you to multiply the result by an 'activity variable' to give a total daily requirement.
To go over a few BMR calculations:
1/ Harris-Benedict formula:
Men: BMR = 66 + [13.7 x weight (kg)] + [5 x height (cm)] - [6.76 x age (years)]
Women: BMR = 655 + [9.6 x weight (kg)] + [1.8 x height (cm)] - [4.7 x age (years)]
This formula is particularly inaccurate - It was derived from studies using lean males in a cold lab many years ago (1919). It is notorious for overestimating calorie requirements, especially in those that are overweight and inactive. IF YOU WANT AN ACCURATE READING, DON'T USE IT!
2/Mifflin-St Jeor:
For MEN: BMR = [9.99 x weight (kg)] + [6.25 x height (cm)] - [4.92 x age (years)] + 5
For WOMEN: BMR = [9.99 x weight (kg)] + [6.25 x height (cm)] - [4.92 x age (years)] -161
This formula was developed in the 1990s. It is much more accurate than the above as it is more realistic in today's lifestyle settings.... However, it still does not take into consideration the difference in metabolic rate as a consequence of high BF%. Thus, once again, it also overestimates needs in highly obese individuals. So - once again, if you use it, be warned it can OVERESTIMATE your needs.
3/Katch-McArdle:
BMR = 370 + (21.6 x LBM)
Where LBM = [total weight (kg) x (100 - bodyfat %)]/100
This is considered the most accurate formula for those who are relatively lean and who have a good understanding of their bodyfat %.
The 'Activity Factor'
An activity factor is something that attempts to quantify your cost of life - it includes work, play, gym, and everything in between! It also includes the average TEF of a standard mixed diet (15%).
1.2 = Sedentary (Little or no exercise and mostly seated during the day, for example - a desk job)
1.3-1.4 = Lightly Active (Basic daily energy expenditure and light exercise or sports 1-3 days a week)
1.5-1.6 = Moderately Active (Moderately active lifestyle / work and Moderate exercise or sports 3-5 days a week)
1.7-1.8 = Very Active (An active and physical job, with hard exercise or sports 6-7 days a week)
1.9-2.0 = Extremely Active (Hard daily exercise or sports and physical job)
Just How Accurate are they?
Unfortunately, nothing is fool proof! So even these estimates are not going to be 'on the mark' in terms of your exact requirements. Most people OVERESTIMATE their activity factor, and UNDERESTIMATE their bodyfat so they also end up eating TOO MUCH. But they will give you a starting figure in terms of roughly how many calories you require to live the life you live and they are also far more accurate than any of those online 'randomly generated' calculators. So what I would suggest you simply find a starting figure then follow your weight over 3-4 weeks. If you remain stable, you've likely found the correct figure.
Using the Above to Recalculate Based on Goals
So, the above go over how much you need to stay the same weight. What about if you want to lose weight? Or what about if you want to gain weight? You obviously need to DECREASE or INCREASE intake based on your goals of INCREASING mass or DECREASING mass.
For this - many people throw around a figure of '500' calories a day. That is - add 500 cals a day to 'gain weight' and remove '500 cals a day' to lose weight. This is based on a false belief that if you subtract 3500 calories a week you will lose 1# a week, and if you add 3500 a week, you will gain 1#. Unfortunately, this is simply not true! Additionally, there is a marked difference as to what impact this figure will have based on the individual involved. For example - if you were to subtract 500 cals/ day from a small requirement of only 1500 calories a day - this is 1/3rd of your total calories, and can leave you far below what you would require to get your basic nutritional needs. Subtracting 500 calories from someone who needs 4000 calories is completely different! Instead?Start by adding or subtracting a % of your required calories.
Generally speaking:
-> to ADD weight: ADD 10-25% of your calories to your total from above
-> to LOSE weight: SUBTRACT 10-30%* calories from your total from above
Then monitor your results and adjust as required.
(* - the reason for the slightly larger figure here is that you get a somewhat temporary down regulation of metabolism as a response to long term dieting, and in order to remain at a good deficit, you may well need to restrict calories further)
Calculating your Macronutrient Requirements
Once you work out how many CALORIES you need to reach your goals you need to work out how much of each particular macronutrient you should aim for.
Contrary to popular methods, I do not feel this should be based on a ratio of total calorie intake such as '30:40:30 or 40:40:20. Your body doesn't CARE what % intake you have for macronutrients. It works in terms of QUANTITY and therefore your level should relate back to your BODY and your bodies NEEDS in terms of LEAN MASS and ACTIVITY!!!
1. Protein: Protein intake is a bit of a controversial issue and the recommendations are constantly changing. In the area of sport, one can also see that the general recommendations given in different areas are also very different! For example, in 'bodybuilding' recommendations are nearly double the 'standard' recommendations given in other sports.
Anyway, the GENERAL sports nutrition guideline based on the information published in recent studies that show that, in the face of ADEQUATE calorie and carbohydrate intake, the following protein intakes are sufficient to maintain 'nitrogen balance' (which means you are able to appropriately repair body tissues):
STRENGTH training - 1.2 to 1.6g per Kg bodyweight (about .6 / pound)
ENDURANCE training - 1.4 to 1.8g per Kg bodyweight (about .8 / pound)
ADOLESCENT in training - 1.8 to 2.2g per Kg bodyweight (about 1g / pound)
BUT they also acknowledge that protein becomes MORE important in the context of LOWER calorie intakes, or LOWER carb intakes OR in highly stressful situations. Indeed recent studies show that levels up to 3g per Kg bodyweight show benefit in terms of stress and physical recovery when faced with highly intense training protocols.
General 'bodybuilding' guidelines? Well - they would be as follows:
- If you guess your bodyfat is AVERAGE = 1-1.3g per pound TOTAL weight
- If you KNOW your bodyfat = 1.3-1.5g per pound LEAN weight
If you are VERY LEAN or on a VERY LOW CALORIE diet protein requirements would be between 2.5 and 3.3g per Kg (1.25-1.5 per pound total weight).
If you are VERY OVERWEIGHT, INACTIVE, or on a HIGH calorie diet then you can decrease intake if desired*, and suggested figures would be ~ 2.2g per kg total weight (1g per pound) down to 1.6-2.2g per Kg total weight (0.8-1g per pound total weight).
Anecdotally? Most find the HIGHER protein intake is better for satiety, partitioning of nutrients to muscle, and blood sugar control. So UNLESS you have reasons not to (that is, medical conditions, or specific GENERAL sports nutrition guides), for those who are looking for changes in physique / body shape, I would suggest the BODYBUILDING values as baselines.
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2. Fats: Generally speaking, although the body can get away with short periods of very low fat, in the long run your body NEEDS fat to maintain general health, satiety, and sanity. However, the guidelines for fat requirements are very hard to find, and most of the time they are 'forgotten' until the end of traditional equations. But there are some studies that suggest the following:
If you are following a 'normal distribution' of intake you should be aiming for something between 1g and 2g per Kg bodyweight (0.4-0.5g per pound total weight) if you are lean, or between 0.8 and 1.8g per kg lean weight (0.35-0.5g per pound) if overweight.
Note 1: Total fat intake is NOT the same as 'essential fats' (essential fats are specific TYPES of fats that are INCLUDED in your total fat intake).
Note 2: For those who are on LOW carb diets, or those who have SPECIAL NEEDS - fat intakes CAN BE HIGHER with values up 2.2g per kg (1g per pound) can be used.
3. Carbs: Although there are no specific 'requirements' for your body, carbohydrates are important for athletes, active individuals, or those trying to gain weight. They area a fuel that helps with workout intensity, health, & satiety (+ sanity). They are also the main source of MICRONUTRIENTS such as vitamins, minerals, and fibre (they include fruits, vegetables, grains, dairy and many other things).
For most individuals, I would calculate requirements based on your calorie requirements as left over from filling the fats & protein needs above. That is:
Carbohydrate Calories = Total calorie needs - ([calories from protein] + [calories from fat))
As both Carbohydrates and Protein contain 4 calories per gram, and fat contains 9 calories per gram, this then means that:grams as above x 9] carbs in grams = above Calories from Carbohydrates = Total calorie requirements - ([grams of protein x 4] + [(grams of fat x 9]). And you divide that total by 4 to get your carbohydrate requirement in grams.
HOWEVER - If you are an athlete - I would actually suggest you CALCULATE a requirement for carbohydrates as a PRIORITY. This is because, for training purposes, carbohydrates are important. So what you would do is calculate your needs for carbohydrates FIRST, then go back and calculate protein requirements, and your fat requirements last. To give an indication for requirements for carbohydrates:
Those who are moderately active: 4.5 - 6.5 g/ kg (about 2 - 3g/ pound)
Those who are highly active: 6.5 - 9 g/ kg (about 3 - 4g/ pound)
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