Last updated on January 17, 2022 at 12:13 pm
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Being Underweight and Gaining Weight
Todayâs world seems only obsessed with losing weight, but the subject of gaining weight is just as important.
Being underweight can be a symptom of a serious underlying condition, especially if weight loss is recent and important. Being underweight can affect the immune system, making the person at risk of developing severe infections, and can expose the skeletal system making the person more prone to bone fractures, along with many other complications.
Whether in athletes that are looking to gain muscle, or in specific populations that are battling health conditions, gaining weight can prove to be something as difficult and as important as losing weight
In this article weâll see how we can determine if a person needs to gain weight, and in case they do, how can they reach their goal?
The BMI
Being underweight means that the personâs weight is considered too low. But whoâs to say that a person is underweight? Surely opinions can vary. So to make this statement as objective as possible, a special measure was developed in the 19th century by Belgian sociologist Adolphe Quetelet:
The BMI, which stands for Body Mass Index, is calculated using the following formulas [1]:
1) The metric system: BMI= weight (kg)/height2 (m2)
2) The imperial system: BMI= 703 x weight (lbs)/height2 (in2)
According to the BMI result, we can define the following categories or ranges:
- BMI < 18.5: Person considered underweight.
- 18.5 <BMI< 24.9: Person considered healthy.
- 25 <BMI< 29.9: Person considered overweight.
- 30 <BMI< 34.5: Person considered obese.
- And BMI> 35: Person considered morbidly obese.
While the BMI is a tool thatâs widely used in medicine and other fields to assess a personâs anthropometric measurements, it is not the best tool to assess a personâs health.
Indeed, the BMI has many limitations, the most important of which is its failure to consider body composition [2].
At the same height, a bodybuilder weighing 200 pounds of mostly muscle and an obese person weighing 200 pounds of mostly fat will both have the same BMI.
Another limitation of the BMI is that it fails to take into consideration the distribution of fat in the body. Adipose tissue in the hips and buttocks of a woman (known as gynoid obesity) has neither the same meaning nor the same consequences as visceral fat around the waist and in the abdomen area (known as android obesity). The first type of obesity is simply a womanâs bodyâs way to ensure that enough is stored to support pregnancy and nursing, whereas the latter is a known risk factor for cardiovascular disease.
Despite its limitations, the BMI can be a helpful tool to determine a personâs health status, especially when paired with complementary tools like measuring waist circumference and body fat percentage or more advanced and precise technology like the DXA scan.
Why are People Underweight?
People can be underweight for a variety of reasons, to summarize:
- They canât meet their energy requirements because they arenât eating enough: âlow energy inputâ.
- Because the food they eat isnât digested, absorbed or metabolized properly: mostly digestive tract issues.
- Or because they canât meet their energy requirements because they burn more energy than they consume: âhigh energy outputâ.
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Low Energy Input:
If a person doesnât meet their daily nutritional requirements for a long period of time, their body will start to consume itself in order to make up for the missing energy and nutrients. First, body fat will be used and turned to energy. After most of the adipose tissue is metabolized, the body will then turn to muscles which will be broken down and used for energy. This process is called catabolism [3].
Being in a state of low energy input can be a caused by anorexia nervosa, an eating disorder that causes a person to intentionally restrict their food intake, or other mental conditions like depression or schizophrenia that decrease a personâs appetite and motivation to eat. States of low energy input can be observed in people suffering from tumors in the mouth, throat or esophagus before they are treated, in specific populations like the elderly, the infants or people with cognitive decline who cannot feed themselves properly and sadly, in parts of the world suffering from famine and food scarcity. Chronic nausea and vomiting can also cause low weight issues, as is seen in cancer patients undergoing chemotherapy. Being underweight can also be genetic, with no discernable reason as a cause.
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Digestive Tract Issues:
Since the digestive system is the interface between the food we eat and our body, it makes sense that any inflammation or problem in the digestive tract will also impact the personâs weight and nutritional profile.
Digestive disorders, like Crohnâs or celiac disease, digestive cancers, and other chronic conditions will affect the digestive systemâs ability to digest and /or absorb nutrients into the bloodstream. As a result of this digestive illness, food will be consumed and then passed on without being absorbed and used for fuel [4]. This essentially translates to being in a low energy input state, and will cause the body to turn to catabolysis to meet energy and nutritional requirements.
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High Energy Output:
In other situations, a person can eat enough, but they will remain underweight because their bodyâs burning too much energy.
This can be the case in people who overtrain or overexercise, in people suffering from cancer [5] or chronic diseases, in which case the body will use a lot of energy to fight off the cancerous cells and the inflammation, or in hyperthyroidism where the bodyâs metabolism is accelerated [6].
How do you Gain Weight?
In adults, body composition is generally measured using the 4 components model, which includes: body fat mass, muscle mass, water mass and bone mass [7]. Bone mass is not something we can intentionally increase, so when we talk about weight gain, it relates to the three other manageable compartments:
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Gaining Water Weight:
Not many people specifically wish to gain water weight. Itâs a rather uncommon situation, usually seen in people who want to quickly add on some pounds to qualify for a specific weight category in a competition for example.
Gaining water weight, also known as water retention, can be caused by an overconsumption of salt or sugars, which are both molecules that tend to trap water inside body tissues [8]. It is a reversible process, the opposite of which being diuresis, or the quick excretion of water. Diuresis, and not fat burning, is usually the process that causes rapid weight loss at the beginning of a low carb diet or after taking diuretic tonics or supplements.
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Gaining Muscle Weight:
Gaining muscle mass is perhaps the most sought after aspect of weight gain. In order to gain muscle mass, two things are needed: putting the muscle under stress in the form of resistance training, and giving the muscle the protein and energy needed to repair the tears caused by the resistance training, thus resulting in bigger muscles and a higher muscle mass.
When training for muscle gain, some itâs important to follow an effective hypertrophy-oriented resistance training program, and to respect rest days and recovery periods [9]. When it comes to nutrition, itâs important to make sure that enough energy, ideally in the form of carbohydrates, is consumed, and that enough protein is consumed all throughout the day to fix the broken down muscle fibers.
Training without the right nutrition will only wear down the body and cause exhaustion, while eating high amounts of carbohydrates and protein without training will result in fat gain, which brings us to our last point:
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Gaining Fat Weight:
Fat gain, although not the healthiest option, can prove helpful in people who are extremely underweight. It is also sought after in certain parts of the world where culturally, curvier people are viewed as more desirable or healthier.
Gaining fat mass is quite an easy process. All is needed is to consume more energy than is required in a day, which would mean being in a caloric surplus, and making sure to remain sedentary, so that this caloric surplus is stored by the body in the form of adipose tissue, also known as fat.
Food groups that provide the body with the most energy are usually carbohydrates and fats. Thatâs why diets that are high in carbohydrates and fats can easily cause fat gain, especially in the absence of sufficient physical activity.
Your Stats:
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MACRO CALCULATOR
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(carb % / protein % / fat %)
Advice to Gain Weight on a Plant-Based Diet:
A good hypertrophy focused resistance training plan is the first step towards building more muscle. Itâs also important to remember that muscles do not grow during the workout, but rather in the recovery window between workouts. So itâs important to rest well.
After the workout comes the nutrition part. The two most important nutrition rules are to consume enough protein throughout the day, and to ensure energy requirements are surpassed, creating a caloric surplus.
Since protein digestibility can be low for plant based protein, itâs important to consume higher amounts of protein than omnivore athletes [10]. Another thing to consider is amino acids availability. Plant based proteins tend to lack in amino acids like methionine and lysine, which are essential for muscle synthesis [11]. Therefore plant based athletes pursuing muscle gain need to make sure they consume protein from different sources, or can turn to supplementation if they judge that their diet is lacking in important amino acids.
Itâs important to consume a surplus of energy, plant based foods tend to be energy sparse and high in water, smoothies can prove to be very helpful as well, since itâs easier to mix a bunch of high calorie and nutrient-rich foods into a smoothie than to consume them on their own. Since fatty foods yield twice as much energy than carbohydrates and proteins, incorporating healthy fats like avocados or nut butters into smoothie is a good way to increase their energy content, while enjoying the benefits of omega-3 fatty acids and fat soluble vitamins.
The Bottom Line
The subject of weight gain isnât given as much attention as that of weight loss. If you are underweight, itâs important to consult with a doctor or a dietitian to make sure the weight loss isnât a symptom of something more severe going on.
When wanting to gain weight, increasing muscle mass is the healthiest route. And that can be attained through a combination of resistance training and sufficient energy and protein consumption.
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