Tips for Healthy Weight Gain: Expert Advice from a Dietitian

Written by Nazish Taban Yazin

Reviewed by Emily Ross

Ensuring that your diet is well-balanced and provides an adequate number of calories tailored to your height, age, and activity level is crucial for maintaining good health. Some individuals who are underweight might not be receiving the necessary calories, protein, and nutrients from their diets, which can put them at risk of malnutrition. This, in turn, can lead to various health issues, including a higher susceptibility to illness and infection, reduced mood, decreased energy levels, diminished muscle strength, and a loss of independence.

Defining Underweight: Being underweight is typically defined as having a body mass index (BMI) of less than 18.5kg/m² for those under the age of 65, or less than 24kg/m² for individuals aged 65 and above. It’s important to note that while BMI is a common indicator, it doesn’t always reflect a person’s overall health. Some individuals may have a low BMI but still be in good health.

Factors Contributing to Being Underweight: Various factors can contribute to being underweight, and it’s crucial to identify the underlying causes early on. Some people may have a genetic predisposition to lower body weight, while others may unintentionally lose weight due to reasons such as:

  • A poor appetite or gastrointestinal issues like nausea or constipation.
  • Illnesses that increase nutritional requirements, such as kidney failure or cancer.
  • Conditions leading to malabsorption, like Crohn’s disease.
  • Difficulty with chewing and swallowing (dysphagia).
  • Side effects of certain medications and medical treatments.
  • Eating disorders.

Risks of Being Underweight: Being underweight poses several health risks, including:

  • Nutritional deficiencies, which can lead to issues like anemia and low energy levels.
  • Fertility problems, particularly in women, affecting menstrual cycles and fertility.
  • Weakened immune system function, making the body more susceptible to infections.
  • Skin, hair, or dental problems due to nutrient deficiencies.
  • Fatigue, which can hinder daily activities.
  • Osteoporosis, a condition causing fragile bones, especially if calcium intake is inadequate.

Tips for Healthy Weight Gain:

  • Consume small, frequent meals and snacks throughout the day (around 6 small meals instead of 3 large ones).
  • Include nourishing snacks like biscuits, cheese, crackers, yogurt, unsalted nuts, or fruits between meals.
  • Add nourishing drinks like milkshakes or smoothies to your diet.
  • Consider high-calorie nutritional drinks such as Ensure or Sustagen.
  • Avoid drinking right before meals to prevent feeling too full.
  • Boost the calorie and protein content of your meals by adding extra ingredients like gravy, spreads, nut butter, fruit, cream, oils, cheese, dried milk powder, sugar, or honey.
  • Eat in a well-ventilated and relaxed environment to stimulate your appetite and focus on your meal.

Enhance Your Meals with:

  • Protein: Protein-rich foods help to improve the body’s strength, immune system and stabilise energy levels and moods. Illnesses such as cancer often cause loss of muscle mass, leaving one feeling weak and vulnerable. Hence, it’s a priority to increase your intake of protein-rich foods to help counteract the effects of the disease and treatments.
  • Carbohydrates: Complex carbohydrates including wholegrains/wholemeals are processed by the body more slowly than their refined counterparts such as white bread and pasta, providing more valuable energy and nutrients. The effect is enhanced when eaten with some protein such as fish, eggs or nuts.
  • Fats: Fats provide a great source of calories, but can also make a dish taste better, which can be just what’s needed when you’re struggling with a lack of appetite. Try adding butter, cream, full-fat Greek-style yoghurt, and olive or avocado oil to dishes.

Unintentional Weight Loss in Older Adults: Being underweight in older adults can lead to severe health problems, including fragile bones and susceptibility to infections. Eating smaller, more frequent meals rather than three large ones can help those with a diminished appetite. Socializing with friends and family during meals can also boost motivation to eat. If cooking is challenging, nutritionally balanced ready meals or meals-on-wheels services can be viable options.

How a Dietitian Can Assist: Dietitians are healthcare professionals with specialized training in nutrition. They can assess individuals at risk of malnutrition, develop strategies to prevent it, and improve overall nutrition status. Don’t hesitate to consult with a dietitian for guidance and answers to your nutrition-related questions.


  1. BBC Good Food – How to Gain Weight: Advice from Dietitian
  2. Nutritionist Resource – Weight Gain
  3. Dietitians Australia – Malnutrition
  4. National Center for Biotechnology Information – Malnutrition


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