The Simple Math to Lose Weight
Disclaimer: This is not medical advice. So don't follow it. This is my opinion. And At time of writing I couldn't be bothered to get you references. N.B. This has become somewhat of an essay, apologies. I will try and put in anchors for you to skip around to parts you need.
This is simply a recount of my own learnings and how I managed to lose approximately 8 kg while training for sport and working a 9-5 "desk" job.
N.B.B.I got tired of writing this after the Energy In Energy Out section, so I may come back to finish it off properly, sorry!
The "ideal" body weight
There are multiple different ways of measuring a person's weight.
For example, if you stood on your scales and read the number, this represents your ACTUAL body weight (ABW).
However, there exist other measures of weight, which are "indicative" of your "true" body weight.
These measures include Adjusted Body Weight (AdBW) and Ideal Body Weight (IBW). There are probably more but I believe the three mentioned are the most common. With ABW and IBW being the most common amongst the general population.
Today I will focus on Ideal Body Weight.
From the best reference available online, Wikipedia:
Ideal body weight (IBW) was initially introduced by Ben J. Devine in 1974 to allow estimation of drug clearances in obese patients
...
The Devine formula for calculating ideal body weight in adults is as follows:Male ideal body weight = 50 kilograms (110 lb) + 0.9 kilograms (2.0 lb) × (height (cm) − 152) Female ideal body weight = 45.5 kilograms (100 lb) + 0.9 kilograms (2.0 lb) × (height (cm) − 152)
Using myself as an example, my approximate height is 175cm, and approximate current weight is 75kg. Substituting these values into the Devine Formula my IBW is approximately 70kg.
Another method of identifying your target body weight, can be done by taking your height (cm) and subtracting 100. This rule-of-thumb method gets pretty close to your IBW and if you were to calculate AdBW, it's also close enough to that. As you would have already calculated my rule-of-thumb target weight is 75kg.
The point I am trying to make is, don't get too caught up with targeting an "ideal" body weight, because there isn't one!
You simply need to aim for a weight somewhere between the IBW and the rule-of-thumb weight, which should both be less than your ABW.
IBW < Target weight < or = rule-of-thumb weight < ABW
The Body Mass Index and Body Surface Area
BMI
Again, I will use Wikipedia to get you an idea of what we're talking about:
Body mass index (BMI) is a value derived from the mass (weight) and height of a person.
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The BMI is a convenient rule of thumb used to broadly categorize a person as underweight, normal weight, overweight, or obese based on tissue mass (muscle, fat, and bone) and height. Commonly accepted BMI ranges are underweight (under 18.5 kg/m2), normal weight (18.5 to 25), overweight (25 to 30), and obese (over 30). When used to predict an individual's health, rather than as a statistical measurement for groups, the BMI has limitations that can make it less useful than some of the alternatives, especially when applied to individuals with abdominal obesity, short stature, or unusually high muscle mass.
So there you go, take BMI as a grain of salt. BMI will tell you that you are big (if you look obese), will tell you that you are big (if you look "normal") and will tell you that you are skinny (if you look "skinny").
This calculation is ONLY a rule of thumb.
BSA
How about this Body Surface Area you talk about Sam? Well...
the body surface area (BSA) is the measured or calculated surface area of a human body. For many clinical purposes, BSA is a better indicator of metabolic mass than body weight because it is less affected by abnormal adipose mass.
Body surface area is calculated by: square-root (( height (cm) x weight (kg) ) / 3600 )
For example: square-root ((175cm x 75kg)/3600) = 1.91 m2
As a rule-of-thumb, most adults should have a BSA of approx. 1.9 m2. Generally people with a BSA > 2 m2 will have a greater BMI.
Again, this is a good rule of thumb. But we can still do better!
Hip to Waist Ratio and Waist Circumference
The SUPERIOR measurements!
These two measurements are provide superior insight into health and wellbeing than the aforementioned BMI and BSA.
Waist size (waist circumference) is an indicator of abdominal obesity. Excess abdominal fat is a risk factor for developing heart disease and other obesity related diseases. A study published in the European Heart Journal April 2007 showed that waist circumference and waist-hip ratio (defined as waist circumference divided by hip circumference) were predictors of cardiovascular events. The National Heart, Lung, and Blood Institute (NHLBI) classifies the risk of obesity-related diseases as high if men have a waist circumference greater than 102 cm and women have a waist circumference greater than 88 cm.
WHR is used as a measurement of obesity, which in turn is a possible indicator of other more serious health conditions. The WHO states that abdominal obesity is defined as a waist-hip ratio above 0.90 for males and above 0.85 for females, or a body mass index (BMI) above 30.0. The National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK) states that women with waist-hip ratios of more than 0.8, and men with more than 1.0, are at increased health risk because of their fat distribution.
I won't put an example in, because I haven't measured myself, but you can see why this would be a superior calculation.
Basically the waist circumference is a direct measurment done with a tape measure. The WHR is a direct measurement of both the waist and hip, you then do waist circumference (cm) divided by hip circumference (cm).
As mentioned by Wikipedia, men should be targeting a WHR of less than 0.9 and women less than 0.85.
Energy In, Energy Out
Before I p roceed to explain this as best I can, there is also an article provided by the Australian Government which sums it up nicely here.
Energy In
The energy which the body takes in and uses is called numerous different things, depending on the form it takes. But all energy which we use is measured in the units of kiloJoules (kJ) (metric) or kiloCalories (a.k.a calories, which is imperial).
1 kiloCalorie (or simply calorie) = 4.18 kiloJoules (kJ)
This is the MOST IMPORTANT concept to remember.
As mentioned, energy takes different forms.
Prior to entering the body, energy comes to us via our diet, in the form of foods. We break food down into 4 groups which each provide DIFFERENT amounts of energy, which are metabolised in DIFFERENT ways (i.e. All kiloJoules are NOT the same!).
The four groups of foods include:
"NO!"
Remember when I said that not all kJ are the same? Well, the reason is their metabolic pathway. Yes, carbohydrates and proteins have the same energy but they have different metabolic pathways!
They are used differently in the body and as such, have different health outcomes!
WARNING: BioChemistry ahead!
As much as I would like to take a deep dive into metabolism and the biochemistry of it, it's probably beyond the scope of most readers.
Basically, we take in the 4 food groups.
Alcohol is the worst, it gets converted into long-chain fatty acids and is inefficient to use. Basically it becomes adipose fat and worsens your health outcomes.
Fats get a bad rap, yes they are the highest in energy, but we can convert them back into usable glucose (the key sugar that is used in all metabolic pathways, it keeps you running). However, only consuming fats can cause you to use the ketolysis metabolic pathway (commonly called the Ketogenic diet). This is hazardous for the body when we naturally fall into this state as it means we have consumed all available quick-acting sugars and are not running on our reserves (fats).
Protein is the best, especially lean (like chicken or kangaroo). It provides plenty of energy and makes you reach satiety (the sensation of feeling full). This energy is also long lasting.
Carbohydrates are a complicated group. In essence, consuming carbohydrates from fruit and vegetables is the BEST way. You get clean sugars and the fibre reduces risk of cardiovascular disease and bowel disease. Carbohydrates from breads, pasta, sugar drinks are not helpful (in-fact, sugary beverages are just as bad as alcohol!).
The lecture featuring Robert Lustig titled Sugar:The Bitter Truth, has a fantastic explanation of how food is utilised by the body and why not all are the same. You can find it here.
Please note, I don't bash sugar, you just need to consider what sugars you are consuming and how that effects you.
Energy Out
So now we have spoken about how we obtain energy, and we've covered how it is metabolised//used. But now, how do we get rid of the energy we take in? Well the answer to that was metabolism.
Humans need energy for basal metabolism which comprises a set of functions necessary for life such as cell metabolism, synthesis and metabolism of enzymes and hormones, transport of substances around the body, maintenance of body temperature and ongoing functioning of muscles including the heart, and brain function. The amount of energy needed for this purpose in a defined period of time is called the basal metabolic rate (BMR). BMR represents about 45–70% of daily energy expenditure, depending on age, gender, body size and composition. Physical activity is the most variable determinant of energy need and is the second largest user of energy after BMR. Humans perform a number of physical activities including the obligatory demands of an individual’s economic, social and cultural environment (eg occupational, schoolwork, housework etc) or discretionary activity (eg energy expended for optional exercise or sport, or in additional social or cultural interactions).
To put simply, we automatically use the energy for maintaining our body and we use the energy for movement. Where most of the energy is used for maintenance. As such the remainder is sport.
A fantastic overview of the metabolic pathways can be found in Prof. James Burnell's "The Text" or on Khan Academy.
Total Daily Energy Expenditure
The Totail Daily Energy Expenditure is the sum energy which you exert including your Basal Metabolic Rate.
Using an online calculator such as TDEE Calculator you can work out how much energy you should be consuming.
For example, after putting in my parameters (including working out 3-5 days per week) my daily energy requirements were: ~2656 calories or 11102 kJ per day. This is for MAINTENANCE!
For sustainable weight loss, online sources (references not included) suggest a 500 calorie or ~2000kJ deficit per day. From my understanding at work, sustainable weight loss is expected to be approximately 1kg per month.
Calories In, Calories Out
The Calories In Calories Out diet (CICO) is nothing new. But it's what we have been talking about today. And it just MAKES SENSE. And essentially all other fad diets, are simply a modification based on the CICO principles. You are what you eat, so eat well!
The 80/20 rule
The 80/20 rule from my personal perspective, is 80% of weight loss happens in the kitchen and 20% exercising. If you watched Sugar: The Bitter Truth, then you know that exercise burns minimal energy compared to what you take in. You may here people saying
You can't run off a MARS bar!. Well, if you don't believe them, check the nutritional information on the pack and then check how many calories you burnt on your 5km run! But as mentioned in the lecture, exercise is essential for maintaining insulin sensitivity and also improves mood. I highly recommend regular exercise.
Keep It Simple Stupid
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