Body Mass Index (BMI) – What Your BMI Should Be for Your Age

 

You’ve probably heard about BMI before in your life, but have you really taken the time to fully understand what this means?

Many people may know it to be some sort of rough indicator of the overall weight appropriateness, since many physicians and other health care physicians often reference BMI numbers. However, it is a grave injustice to not understand what BMI really is, or some of the common misconceptions about it.

In addition to giving you a fair average of how close to ideal weight you are for your height, it can also give an indication of your susceptibility to certain health conditions later in life, or your relative risk of a disease.

But not to worry-In this article, we will discuss everything you need to know about BMI, and steps you can take to help ensure that you fall within a normal range bracket in most circumstances

What exactly is BMI?

BMI is an abbreviation that simply means body mass index. Unlike many confusing medical terms used by healthcare professionals, BMI is a relatively simple and straightforward concept.

To put this the shortest way, it is a simplification representing your body mass per meter square of height.

So, for example, a BMI of 20 means that you possess approximately 20 kg/m² of height.

Commonly used as a diagnostic tool to determine where you fall on the scale of being classified as normal, overweight, or obese, for the general population BMI is well accepted and a reliable indicator of where you stand.

Based on these estimates of using BMI, the United States Center for Disease Control averages that over 33% of adults classified as obese.

This has several ramifications on national healthcare systems, since they also estimated that just 10 years ago in the year 2008 more than $147 billion was expended on healthcare, with the major portion of that allocated to managing chronic morbidities directly related to having a high BMI, or being overweight/obese.

Obese individuals are also much more likely to pay higher insurance fees, averaging $1400 more than normal weight individuals per year.

This may not seem like a lot at first, but when you multiply that over several years (and that fact that at risk individuals may pay far more than this), you can see how your weight is a direct financial burden.

What is Considered a Good BMI to aim for as an Adult?

Even though BMI numbers are generally not set in stone, there is significant variance based on several factors, with major one of these being ethnicity.

For instance, people with African ancestry are considered the most likely to be obese, followed by people that identified as Latino, White, then subsequently other races, lastly those that are Asians.

Your general BMI also increases as you age, so it is much more likely for a person that is middle aged to have higher BMIs along with other comorbidities.

According to the World Health Organization WHO, certain guidelines are established in order to help classify individuals ranging from severely underweight to obese classes, otherwise known as hyper- obese.

BMI ranges include the following:

Very severely underweight – BMI less than 15
Severely underweight – BMI ranging from 15 to 16
Underweight – BMI between 16 to 18.5
Ideal weight – BMI ranging from 18.5 to 25
Overweight – BMI ranging from 25 to 30

Obese – BMI of 30 and over, with increasing BMI in multiples of five being classified as classes ranging from the number 1 to 6 (so obese class 1, obese class 2 etc.)

BMI is not usually indicated for measuring weight in children, but rather compared against percentile ranges for children of the same gender and age.

Even though most countries follow the WHO established ranges, many have modified these numbers to accommodate for localizations and differences in ethnicity and population demographics.

Calculating Your BMI

Calculating your BMI at home not that difficult, even though it is probably much more convenient to use one of the readily available calculators online to simply plug in your numbers and have your BMI value returned.

However, for those of you that are mathematically inclined, the formula is simple: your weight in kilograms divided by your height in meters squared gives you your BMI.

To put this into example let’s use a simple one if you weigh 68 kg, and are 1.65 m tall, then the BMI formula = 68 divided by 1.65 multiplied by 1.65 , which gives the answer 24.98.

In this case, the individual falls in the normal range which ends at 25.

It is important to keep in mind that women generally have higher BMI than men, based on the fact that their bodies retain more fat in preparation for childbearing.

This may change after menopause when the effects of estrogen are significantly reduced.

Men carry a greater proportion of muscle and are more likely to possess lower BMI owing to higher metabolic rates.

What Type Of Complications Can Having A BMI Cause?

Though there is not a clear-cut relationship between high BMI and the risk of morbidity and mortality, there is clear correlation to the fact that the higher BMI may increase your risk of negative health outcomes significantly, with many people possessing higher BMIs having metabolic problems.

In general, the higher your BMI is, the greater your risk of developing the following:

Type II Diabetes – people with higher BMI that are classified as overweight or obese are more likely to overeat and have poor blood glucose control, based on a reduction in overall insulin sensitivity. Eventually, this loss of insulin efficacy impairs the absorption of glucose by muscle cells, with excess being stored as fat.

A stage is reached where insulin is unable to fulfill its functions, resulting in chronically elevated blood glucose readings.

At this point, extensive damage to the vascular and nerve networks of the body may be possible which then paves the way for a series of other conditions to follow.

Management of blood glucose is extremely important, with many people not knowing that they are diabetic until a doctor’s visit for a complication. This can include an injury that is not healing, unexplained weight loss, or changed in sexual function to name a few.

Heart Disease – possessing higher BMI also increases your risk of heart disease significantly, by a few different mechanisms.

For instance, people that have higher BMIs are more likely to have elevated cholesterol and triglyceride levels, which by itself is bad enough and usually signals for medical intervention to be made, but when combined with the fact that insulin and blood glucose dysfunction may also be present, the risk of atherosclerotic plaque deposits blocking critical blood vessels is increased significantly.

In addition to this, the inflammation caused by the presence of excess glucose can also increase blood vessel stiffness, and in the event that a large enough part of atherosclerotic plaque dislodges and breaks off, a blood clot can form leading to a stroke.

Arthritis – while arthritis is primarily viewed as an old people disease, a larger and larger number of younger people are being diagnosed with the condition based on their BMI. It’s no surprise when you think about it, since having to bear more weight puts more pressure on your joints. Eventually, wear-and-tear is accelerated under the influence of excessive weight, causing possible damage to the cartilage and structures lining your joints.

If you already have joint pain or have been diagnosed with arthritis, your best bet is to start losing the weight and partake in low intensity exercise that does not cause joint pain. These sorts of activity include swimming, biking and using elliptical exercise machines.

Joint support supplements that contain glucosamine, chondroitin and collagen can also help to alleviate significant amounts of discomfort you may be feeling.

Cancer – often times, people with high BMI and excessive levels of body fat experience greater amounts of inflammatory processes. Over time, these inflammatory processes may cause damage to cells or even DNA itself, leading to a greater likelihood of cellular replication errors.

Mutations occur every day in the human body, that is the fact. But an increasing frequency of mutations leaves less space that one too many might occur that is resistant to natural destruction by the immune system, leading to growth of a tumor.

Cancer treatment in overweight/obese patients is generally more difficult as well, especially with relation to the surgery aspect. Prognosis is generally poorer for people with hormone dependent cancers and based on the fact that it is more difficult for the body to support the excessive tissue at this time.

Fatty Liver Disease – in the past fatty liver disease was limited to people that consumed alcohol excessively, resulting in alcoholic fatty liver disease. These days, arguably a greater number of people are diagnosed with a condition known as nonalcoholic fatty liver disease, caused by an excessive accumulation of fat in the liver as a result of diet, and not alcohol consumption.

Fatty liver disease may not be serious in its early stages, but eventually it causes chronic liver inflammation, elevated liver enzymes that metabolize foods and drugs, and can even lead to permanent scarring of liver tissue, reducing functionality and progressing to cirrhosis.

This is a dire outcome, and one that usually requires a liver transplant at this point. Luckily, fatty liver disease can be remedied by getting your BMI in check and reducing your bodyweight. Reducing your consumption of fast digesting carbohydrates; especially high fructose corn syrups and processed fats also goes a far way in helping to overcome this problem.

Insomnia and Sleep Apnea – there was a study conducted many years ago correlating the size of an athlete’s neck, or more specifically its circumference, with an increased risk of obstructive sleep apnea.

As the years progressed, it was also found that these correlations also apply to obese or overweight individuals, who may have excessive fat, not muscle, surrounding the neck and compressing the airways during sleep.

Obstructive sleep apnea causes a temporary inability to breathe during sleep, which usually causes individual to wake up alarmed and panting for breath. In severe cases, sleep apnea may even result in death during sleep if breathing fails to resume normally.

Depression – while people with high BMI end up invariably experiencing neurotransmitter and brain chemical imbalances, depression itself may manifest from feelings of worthlessness, or not being good enough after being classified as too fat.

Medical treatment for depression exists, but the majority of common approaches leave a lot to be desired. It is a self-propagating cycle that can foster secondary behavioral disorders including generalized anxiety, binge eating disorder and even fostering suicidal tendencies.

There is no proven consensus that possessing a high BMI will cause you to develop diagnosed depression, but being overweight/ obese is something many people struggle with especially when it comes to social acceptance.

What Causes An Increase In The Risk Of Having High BMI?

One of the primary factors that influence your BMI is dietary and lifestyle habits. In general, your BMI is likely to shoot up when you consume more calories than you expend consistently on a day-to-day basis, causing retention of excess calories as fat.

There are also several other factors that contribute to you having a greater BMI, including:

Consumption of Significant Amount of Processed Foods – diets that revolve around processed foods, including carbohydrates and fats, which are low in vegetables and fruits are more likely to cause weight gain, based in part on energy density of these foods, and the fact that they do very little for actual nourishment of cells.

Fruits and vegetables in contrast are considered low-calorie, possess significant amounts of fiber which can help to suppress appetite meaning that you eat less over the course of the day. Aim for some vegetables with each meal, and a piece or two of fruit daily.

Your Activity Level – do you sit in front of a computer screen all day? If this sounds like you, then chances are you probably do not burn a lot of calories.

This is a recipe for weight gain and subsequent increases in BMI, owing to the fact that high stress may also cause you to eat more fast food. The lower your activity level, the greater the likelihood of your BMI going up.

Certain Diseases or Medical Conditions – if you have diabetes or metabolic syndrome, you are likely to consistently increase your BMI and weight gain based on the fact that metabolic processes are less than ideal, and glucose dysfunction fosters an environment conducive for weight gain.

This, along with other conditions that affect hormonal equilibrium can also lead to rapid weight gain. Even mental health conditions such as depression can cause an increase in BMI by virtue of it causing loss of motivation and lethargy.

What Can You Do That Optimize Your BMI?

Getting your BMI within the normal range or as close to normal as possible should be your goal, given that you are considered normal. More on what normal means later on.

But if you wish to start making positive changes right now, try to follow a few of these tips:

Toss out the Junk – anything packaged in your house is likely processed. Processing usually means that natural foods have your their structure of modified in an effort to extend shelf life and palatability. This means that your favorite treats may be extremely high in sodium, sugar or trans fats, and have little to no real nutritive value.

You should start by getting rid of any temptation you have around your house, including the dreaded soda. This includes diet soda as well, which even though indicating 0 cal on the label, still causes unfavorable metabolic changes that will in the long run predispose you to developing diabetes and other health maladies.

This also includes reducing your reliance on fast food. Make it your goal to cook your own food. Not only does this help you know what you are consuming calorie wise, but you will also be able to consume any option you deem as healthy. If you find it challenging to cook food on workdays, you can either perform weekend meal prep- storing your food in the fridge or freezer for later in the week, or readying the necessary ingredients so that during the week you only need to combine and cook.

The best way to get control of your BMI is to know exactly what you consume, and with takeout there will always be something that you just can’t control.

Eat More Protein – one of the best things you can do in an effort to reduce your BMI, or even increase it for that matter if you are underweight, is consume more protein. Protein is the body’s key building block, being fragmented into individual amino acids and used where needed. This includes recovery of cellular components that boost immunity, and supporting muscle protein synthesis, very important to your metabolic rate.

People with greater amounts of muscle mass have higher resting metabolic rates, translating to a larger number of calories used over the course of the day for the carrying out of basic body functions.

Protein also has the added benefit of a high thermic effect, meaning that a large portion of the calories it yields upon consumption is used for processing of the food, and not added to your calorie bottom line.

Go Carb Free – the low carbohydrate way of eating is undoubtedly one of the best ways to effect rapid and radical weight loss. Indeed, it is not for the faint of heart, as cravings and hunger pangs are sometimes extreme, but if you manage to successfully reduce your carbohydrate consumption to a great extent, weight loss will inevitably follow.

The metabolic changes that occur when glucose is limited means that the body turns to stored fat for energy in these times. This is of course, a good thing, since by digging into the stored amounts of body fat, your weight will go down in the process.

The ketogenic diet is particularly effective for rapid weight loss, and is more sustainable than a mere starvation diet.

More Activity – this means getting more actual exercise, and doing anything that is considered physical activity in an effort to meet the minimum recommendation of 150 minutes of moderate intensity aerobic exercise per week, such as walking or playing tennis.

If you are unable to be active at your job, try to walk a few blocks home by taking an early bus stop, or walking around the block a few times every day over the course of the week.

Keep in mind this is also a minimum recommendation, so if you can manage more by all means please do.

You should also not underestimate the importance of strength training, as muscles atrophy over time if they are not being challenged. Preserving your muscle mass is key to keeping your metabolic furnace working well into middle and advanced age to reduce your risk of that BMI value creeping up.

Get More Sleep – The average adult requires between seven and nine hours of sleep likely, even though a significant number of them fall well short of this night after night. Chronic sleep deprivation has many negative health outcomes, including increased risk of high blood pressure, depression, heart disease, and obesity.

The reset mechanisms that are active during sleep are not fully utilized, and as a result the hormones and neurotransmitters function at levels that are either sub optimal or way too high.

Perform Stress Management – You cannot avoid all stress, as it is a necessary survival mechanism embedded in our DNA. However, it is the fact that far too many of us grapple with excessive stress day after day, whether that be from personal issues, your job, or just anxiety of things that may never occur.

High stress levels often result in over secretion of the stress hormone cortisol, which is pro-inflammatory in nature and sets about a cascade of native outcomes.

In turn, there is an increased risk of heart disease and diabetes, even cancer risk is significantly amplified under the influence of excessive cortisol.

Try to master stress relief techniques – meditation rules the roost here, as do martial arts disciplines such as tai chi, or even yoga. Find what relieves you and soothes, and be sure to practice it often.

The Shortcomings Of Measuring BMI

Remember how we mentioned not too long ago that BMI is an effective tool for the majority of normal adults? Well, turns out there are segments of the population that are not considered normal.

Who are referring to? These following groups:

Athletes – have you ever seen the amount of muscle mass a bodybuilder carries around? There are bodybuilders waiting in excess of 250 pounds, packed with muscle and very low amounts of body fat. Do the BMI classifications hold true for such categories of people? No, they do not. This is because having a high BMI as an athlete is a different ballgame altogether, since these individuals possess high muscle density, and lower body fat than normal people.

They may also have much lower relative risk factors for the conditions previously outlined, making BMI a less than optimal tool for averaging weight to height ratio for these individual.

Athletes typically use skin calipers to measure body fat, which in the grand scale of things is typically low.

Pregnancy – would you classify a pregnant woman as obese? Not Necessarily. This is also why BMI should not be used while a woman is pregnant, or even nursing.

An obstetrician will likely keep an eye on other values critical to metabolic health during pregnancy, including percentile norms and amount of weight gained during the actual pregnancy, but BMI is not to be utilized at this time.

Age – the older you get, the less accurate BMI reflects your overall health. This is especially true in people older than 65 years of age who may have skewed proportions of muscle to fat. Natural sarcopenic muscle loss is extremely common, and when coupled with common morbidity or other health conditions, BMI values are likely to see much higher than they really are.

Ethnicity – Asians do not fit the mold that BMI applies to quite often, based on the fact that analyzing a large sample base would indicate that many of them are underweight, while in fact they are normal. This is exactly why modified guidelines are usually implemented in Pacific and Asian countries, as the genetic makeup of these individuals often causes them to have less lean body mass and body fat. BMI values are usually reduced in like manner. For example, in Japan having a BMI up to 23 classifies you as normal, anything over jumping straight to obese.

Alternatives To BMI

If you fall into one of these categories that BMI is less than ideal for averaging your overall fitness and health, you may be better served by seeking to maintain an optimal body fat percentage. For women, this may range from 25 to 31%, and for men it’s usually between 18 and 25%. For athletes this number is usually much lower, typically maxing out at about 20% for both women and men.

In Summary

BMI is a great tool for diagnosing your relative risk of disease, and gauging in a person’s overall fitness and health. Having a high BMI that classifies you as overweight or obese should be an eye-opener for you to actively try to reduce your body weight, and on the opposite end of the spectrum, having a low BMI that makes you underweight should mandate intervention with a dietitian or nutritional specialist.

You should strive to be as close to normal BMI is possible if you fall within the generalized normal population, by instituting dietary and other lifestyle changes. At the end of the day, it is important to keep in mind that each individual’s different genetic mix means that you might not look the way you want, but you can still achieve the pinnacle of health and fitness.