Being too skinny can be just as dangerous as being overweight. While society often promotes thinness as the ideal, being underweight can lead to health problems. So when does thin become too thin?
What are the causes of being underweight?
Some common causes of being underweight include:
- Genetics – Some people are just naturally thin and have a fast metabolism.
- Eating disorders – Conditions like anorexia nervosa or bulimia can lead to excessive weight loss.
- Diseases – Certain medical conditions can cause poor absorption of nutrients or increased metabolism resulting in unintentional weight loss.
- Hyperthyroidism – An overactive thyroid gland can accelerate metabolism leading to weight loss.
- Cancer – Cancerous tumors can release chemicals that change metabolism and cause weight loss.
- Medications – Certain medications may have weight loss as a side effect.
- Smoking – Smoking increases metabolism and often leads to appetite suppression.
- Drug/Alcohol abuse – Substance abuse can alter appetite and physiological processes resulting in low body weight.
- Stress – High levels of stress can suppress appetite and change metabolism.
What are the health risks of being underweight?
Being underweight comes with a number of potential health risks including:
- Malnutrition – Not getting enough calories or nutrients can lead to vitamin/mineral deficiencies.
- Weakened immune system – Lack of nutrition inhibits the immune system, increasing risk of infections.
- Fertility issues – Women who are underweight may stop ovulating and have difficulty getting pregnant.
- Osteoporosis – Too little body fat and malnutrition increases bone loss over time.
- Anemia – Underweight individuals are at risk for iron deficiency anemia.
- Organ failure – Being severely underweight strains organs like the heart and lungs.
- Poor wound healing – Nutrient deficiency impairs the body’s ability to repair itself after injury or surgery.
- Growth issues – Being underweight can slow development and growth in children/teens.
- Early mortality – There is an increased risk of early death from medical complications.
What are the physical signs of being underweight?
Here are some physical indicators that someone may be underweight:
- Prominent bones – Protruding collarbones, shoulder blades, ribs, vertebrae or pelvic bones indicate low body weight.
- Thin limbs – Very slender arms and legs with little muscle/fat.
- Sunken cheeks/temples – A gaunt, hollowed appearance in the face.
- Thin hair/hair loss – Nutrient deficiency can lead to thinning hair or hair loss.
- Pale skin – Lack of subcutaneous fat makes skin appear pale.
- Poor temperature regulation – Difficulty maintaining body heat due to low fat reserves.
- Lanugo – Fine, downy hair that grows to compensate for lack of body insulation.
- Blue hands/feet – Poor circulation causes hands/feet to often feel cold.
- Dizziness/fainting – Low blood pressure from being underweight can cause dizziness.
- Irritability – Hunger and nutritional deficiency can cause mood changes.
What is the ideal weight for my height?
The ideal weight depends on several factors including age, gender, muscle mass, and bone structure. However, body mass index (BMI) is a simple way to evaluate if your weight is in a healthy range. Here are some general BMI guidelines:
BMI Categories:
- Underweight = BMI below 18.5
- Normal weight = BMI 18.5 – 24.9
- Overweight = BMI 25 – 29.9
- Obesity = BMI over 30
To calculate your BMI, divide your weight in kilograms by your height in meters squared. Or use this BMI calculator:
Here are healthy weight ranges based on height:
| Height | Healthy Weight Range |
| 5’0″ (152 cm) | 97 – 123 lbs (44 – 56 kg) |
| 5’3″ (160 cm) | 106 – 132 lbs (48 – 60 kg) |
| 5’6″ (167 cm) | 114 – 141 lbs (52 – 64 kg) |
| 5’9″ (175 cm) | 123 – 150 lbs (56 – 68 kg) |
| 6’0″ (183 cm) | 132 – 159 lbs (60 – 72 kg) |
These weight ranges are just general guidelines and may vary depending on your frame size and muscle mass. The best way to determine if your weight is too low is to look for physical signs/symptoms of being underweight. Talk to your doctor if you have concerns about your weight.
I think I may be underweight. What should I do?
If you suspect you are underweight, here are some steps to take:
- See your doctor – Get an exam and have tests done to check for underlying medical issues.
- Consider therapy – If an eating disorder or mental health issue is contributing, seek professional counseling.
- Boost nutrition – Focus on high calorie, protein-rich foods and nutritional supplements.
- Exercise – Light activity can help increase appetite and build muscle mass.
- Keep a food journal – Record meals and snacks to ensure adequate calorie intake.
- Set meal reminders – Stick to a meal schedule with 5-6 small meals throughout the day.
- Manage stress – Adopt relaxation practices to lower stress hormones that inhibit hunger signals.
- Join a support group – Connect with others facing similar struggles for motivation and accountability.
- Be patient – Give your body time to recover and regain weight in a healthy way.
The goal is to aim for slow, gradual weight gain until you reach a healthier weight recommended by your doctor. Sudden extreme weight gain can have negative effects. With professional support, determination, and self-care, you can overcome the challenge of being underweight.
What does it mean to have a “fast metabolism?”
People often attribute being underweight to having a “fast metabolism.” But what does that really mean? Your metabolism refers to all the chemical processes in your body that convert food into energy. A fast metabolism simply means you burn calories at a faster rate. Here’s a closer look at metabolic rates and what influences them:
- Basal Metabolic Rate (BMR) – The minimum number of calories needed to perform basic physiological functions while at rest. Accounts for 60-75% of daily calorie burn.
- Age – Metabolism slows as you get older.
- Gender – Men often have a higher BMR than women.
- Genetics – Some inherit a naturally faster metabolism.
- Muscle Mass – More muscles require more energy, increasing metabolism.
- Physical Activity – Exercise/movement burns extra calories and boosts metabolism.
- Diet – Eating more protein and fewer carbs can increase metabolism.
While a fast metabolism is largely influenced by genetics, there are ways to help speed it up, such as exercise, strength training, eating protein and staying hydrated. However, it’s important to rule out underlying medical conditions before simply attributing being underweight to a fast metabolism.
What is the best diet for an underweight person?
If you are underweight, focus your diet on the following strategies to gain lean weight safely:
- Eat 5-6 small meals/snacks throughout the day – Keeps metabolism boosted.
- Emphasize nutrient-dense calories – Choose whole grains, healthy fats, lean protein, fruits and vegetables.
- Increase healthy carbs – Whole grains, starchy vegetables and fruits provide energy-rich calories.
- Consume plenty of protein – Protein foods build/maintain muscle and increase metabolism.
- Drink energy/protein shakes – Liquid meal replacements provide nutrition in a calorie-dense form.
- Cook with healthy oils – Use olive, coconut or avocado oil to add calories to meals.
- Snack on nuts and nut butters – They are high in protein, fiber and calories.
- Eat full fat dairy – Opt for whole milk, yogurt and cheese over low-fat options.
Avoid empty calories from junk foods, sweets and fried foods. Focus on a whole food diet rich in lean proteins, fruits, vegetables and whole grains to gain weight in a healthy way. See a registered dietitian if you need help creating a personalized meal plan.
What types of exercise help underweight people gain muscle?
For underweight individuals looking to put on muscle, these are the best types of exercise:
- Strength Training – Lifting weights is optimal for building lean muscle mass. Target all major muscle groups 2-3 times per week.
- Calisthenics – Push-ups, planks, squats, lunges and sit-ups use body weight as resistance to build muscle.
- Yoga – Poses like downward dog, plank and chair pose help strengthen muscles.
- Pilates – Focuses on core strength and improves posture/balance.
- Swimming – Provides a full-body workout to build muscles without high-impact stress on joints.
- Interval Training – Alternating between high and low intensity bursts aids muscle growth.
- Resistance Bands – Bands add resistance to build strength with options for varying difficulty.
Aim for 30-60 minutes of strength-training 3-5 days per week along with nutrition tactics to spur muscle growth. Be sure to give muscles a day of rest between strength workouts and consult a trainer if you are new to weightlifting.
What are signs my child is underweight and how can I help them?
If your child appears underweight, look for these warning signs and take steps to help them reach a healthy weight:
Signs of Underweight in Children:
- Very prominent ribs and bones
- Thin limbs and muscle wasting
- Lack of energy/tires easily
- Feeling cold frequently
- Poor immune function/gets sick often
- Delayed growth/puberty
- Picky eating or lack of appetite
How to Help an Underweight Child:
- Consult pediatrician to rule out underlying illness
- Provide small, frequent, nutrient-rich meals
- Keep calorie-dense snacks on hand like nuts, cheese
- Offer smoothies and shakes for extra nutrition
- Find physical activities they enjoy to build muscle
- Consider safe dietary supplements if diet lacks key nutrients
- Practice patience and positive encouragement at mealtimes
- Schedule annual well-child check-ups to monitor growth
Gradual weight restoration is crucial for avoiding long-term complications. With your pediatrician’s guidance, keep interventions positive and focus on health, not just weight.
Conclusion
Being underweight can negatively impact health and quality of life. While some people are naturally thin, it is important to rule out underlying medical causes for low weight like hyperthyroidism, eating disorders, or chronic disease. Indicators like a thin face, prominent bones and poor circulation should raise concern. Calculate your BMI and aim for a healthy range based on your height. To gain weight safely, eat frequent small meals with plenty of proteins, carbs and healthy fats. Incorporate strength training to build muscle mass. See a doctor for a full evaluation and work with a dietitian or nutritionist to create an individualized healthy eating and exercise plan to achieve your goals. With determination and support, gaining weight in a healthy manner is certainly possible.