A person’s build depends largely on genetic factors, which is why it is difficult for a naturally thin person to put on weight. The human body can change to a limited extent through weight training and increased food intake. Gaining or regaining weight can be just as difficult as losing weight. When done in a smart, healthful way, many of the same basic principles apply to both gaining and losing weight.

It is important to consult with your doctor to make sure that your weight-gaining tactics are healthy and appropriate for you.

Reasons for lack of weight gain

Some common reasons why a person may find it hard to gain weight include:

  • genetics
  • not eating enough
  • having a very physically active lifestyle or job
  • overexercising

Please note that some people are too thin because of a disability, eating disorder, substance abuse, or serious medical condition – these conditions are not addressed in this fact sheet.

Consult with your doctor before trying to gain weight

Always see your doctor before you start any weight-gain program. Your doctor can:

  • give you a check-up to rule out the possibility of an underlying medical condition that may be causing your thinness, such as hyperthyroidism
  • suggest an appropriate weight goal for your height and build
  • assess your diet and physical activity levels
  • advise on diet, exercise and lifestyle changes that will encourage weight gain
  • refer you to other specialists, such as a dietitian, if necessary.

Eat more for weight gain – quality first, quantity second

Being underweight usually occurs when energy (kilojoule) intake is less than the energy used. In other words, you need to eat more in order to gain weight.

The secret to healthy weight gain is to make all your kilojoules as nutrient-rich as possible. Consuming more empty-calorie foods like soft drinks and chips is not a successful way to build muscle, strengthen bones or repair tissue after surgery.

Suggestions include:

  • Use a kilojoule-counter book to calculate how many kilojoules you eat on an average day. The amount may be smaller than you think.
  • Eat three good meals every day. Give yourself slightly larger serves if you can.
  • If you have a small appetite, eat five to six times a day. Drink fluids before and after meals, but not with them. This helps leave more room for food.
  • Successful weight gain requires that you increase your daily intake of carbohydrates. Avoid low carbohydrate diets.
  • Eating vast amounts of dietary protein won’t make your muscles grow faster and will put unnecessary pressure on your body, especially your kidneys. Avoid high-protein diets.
  • A healthy snack may include fruit, yoghurt, muffin, rice pudding, low-fat custard, milkshake or liquid meal supplement.
  • Avoid high-fat junk foods. Instead, choose nutritious high-fat foods such as avocado or nuts.
  • Top your usual foods with some concentrated calories, like grated cheese. Spread peanut or almond butter on a wholegrain muffin.
  • Prepare hot oatmeal or other cereal with milk, not water. Add powdered milk, honey, dried fruits or nuts after cooking.
  • Garnish salads with healthy oils such as olive oil, whole olives, avocados, nuts and sunflower seeds.
  • Pump up soups, casseroles, mashed potatoes and liquid milk with one to two tablespoons of dry milk powder.

Resistance training for muscle gain

Resistance training promotes muscle growth. Examples of resistance training include the use of free weights, weight machines, your own body weight or resistance bands. Suggestions include:

  • Train just two or three times per week to give your muscles time to recover. If you’re tempted to train more often, remember that muscle growth occurs during recovery.
  • Choose compound exercises that work multiple major muscle groups, for example, the squat and bench press.
  • Make your workouts short and intense rather than long and leisurely.
  • Don’t waste your time or money on powders, pills and products that claim to increase muscle mass. These claims are not scientifically proven.
  • Seek professional advice. A gym instructor, personal trainer, exercise physiologist or physiotherapist will help make sure you are doing each exercise correctly. Good advice will increase your gains and reduce your risk of injury.

Lifestyle adjustments for weight gain

Suggestions include:

  • Be prepared to eat when you are not hungry.
  • Use a timer to remind yourself to eat every two hours.
  • Try to make your additional eating sessions as appealing as possible. For example, stock the fridge and cupboard with snack foods you love.
  • Eat small serves of protein foods before and after each resistance training session to help promote muscle growth.
  • Accept that an increase in food intake may cause bloating or gas.
  • Be prepared to gain some fat as well. It isn’t possible to increase muscle mass without also increasing body fat.

Track your weight gain progress

Tracking your progress helps to boost motivation. Suggestions include:

  • Keep a diary to monitor your kilojoule intake and training schedule.
  • Be consistent. Weight gain requires that you increase your daily food intake every day. It may help to write up meal plans.
  • Make sure your goals are realistic. For example, an increase of a few kilos may take a year to achieve. Putting on lean body weight takes time, so don’t be disappointed with small gains.
  • See your doctor regularly to assess your progress.

Where to get help

  • Your doctor
  • Dietitians Association of Australia Tel. 1800 812 942
  • ESSA Exercise & Sports Science Australia Tel. (07) 3862 4122
  • Physiotherapist
  • Qualified gym instructor
  • Qualified personal trainer

Things to remember

  • Gaining lean body weight is a slow process that takes months and years rather than days and weeks.
  • See your doctor before starting any weight-gain program.
  • To gain weight, you must eat more and stimulate muscle growth.
  • Don’t waste your time or money on powders, pills and products that claim to increase muscle mass.