Evidence checked: 19 July 2026
Written by Charles Gumbley, BHSc (Clinical Nutrition), DipHSc (Western Herbal Medicine).
The right approach depends on why someone is not gaining weight. A protein supplement can fill a genuine gap, a mixed drink can add kilojoules, and creatine can support training. None can identify the cause of unexplained weight loss, replace meals or guarantee new muscle.
If weight has fallen without trying, seek medical assessment, not a mass gainer. Malnutrition can affect people at any body size, especially older adults. Causes include poor appetite, swallowing problems, restrictive eating, medicine effects, malabsorption, thyroid disease, diabetes, chronic illness and eating disorders.[1,2]
Medical disclaimer: This is general education, not personalised advice. See a GP and Accredited Practising Dietitian before a program if weight loss is unexplained, you have a health condition, take medicines, are pregnant, are under 18 or compete under anti-doping rules.
Clinical bottom line: A balanced diet and suitable training plan do most of the work. Dietary supplements address a defined gap. Rapid promises, bodybuilding pills and large serving claims do not establish safe or useful change.
Before choosing a weight gain supplement
Clarify the goal. Restoring weight after illness, treating malnutrition, supporting growth and building muscle are different situations. A scale increase can be muscle, fat, fluid, glycogen or gut contents; it does not automatically show better health.
Consult your doctor promptly for unplanned loss, persistent vomiting or diarrhoea, swallowing difficulty, bleeding, severe pain, marked thirst and urination, fever, night sweats, a lump, fainting, weakness or confusion. Low appetite, fear of gaining weight, purging, compulsive exercise or restrictive eating also warrant respectful assessment.
Severely malnourished people or those who have eaten very little can develop refeeding syndrome when nutrition restarts. Australasian consensus recommends clinical risk management; a self-directed high-calorie shake plan is not appropriate.[3]
Healthy weight gain starts with food and a plan
Weight gain requires more usable energy than the body expends, adequate protein and, when suitable, progressive weight training. Better Health Channel advises medical review, nutrient-rich kilojoules and recognising that lean tissue changes slowly.[1]
Food-first options include regular meals and snacks, full-cream dairy or fortified alternatives, eggs, legumes, nuts, avocado, olive oil, grains and energy-dense additions. An APD can adapt these for allergies, coeliac disease, diabetes, kidney disease, gastrointestinal symptoms or limited appetite.
The largest calorie surplus is not necessarily better. Calorie intake and protein needs vary with size, activity, illness, appetite and weight gain goals. Counting may be unsafe in an eating-disorder context. People who struggle to eat may need texture, timing or symptom changes before a powder.
Which are the best weight gain supplements?
Scroll sideways to read the full table →
| Option | Where it may fit | What it cannot establish |
|---|---|---|
| Protein powder | Convenient protein when food intake does not meet an assessed need | Weight change by itself or superiority to protein-rich food |
| Mixed macronutrient or mass gainer | Extra carbohydrate and protein when volume, appetite or schedule is a barrier | That a large labelled serving is appropriate for you |
| Creatine monohydrate | Selected healthy adults doing resistance training or high-intensity sport | Treatment for low weight, illness-related loss or malnutrition |
| Oral nutrition supplement | Clinician-selected support when ordinary food is insufficient | A universal retail solution or meal plan |
The supplements listed are examples of roles, not a shopping list. A calorie or protein gap should be identified first. The right option solves that gap without displacing food or needed care; many people need none.
Protein powder and muscle growth
Protein provides amino acids for muscle protein synthesis and tissue maintenance. A review of 49 resistance-training trials found modest additional average fat-free-mass and strength improvements with supplemental protein. The effects of protein supplementation varied; pooled increases in lean body mass did not guarantee an increase in lean muscle mass for each person. Benefits diminished when daily protein intake was sufficient.[4]
That supports filling a gap; it does not make whey protein a stand-alone gainer. Whey, casein, soy protein isolate and plant blends differ in amino acid profile, allergens, digestibility and composition. A shake may contain fewer kilojoules than a mixed meal, so protein alone may not raise body weight.
Check labels for allergens, stimulants, sweeteners and duplicated vitamins. Kidney disease, fluid restrictions and metabolic conditions need individual advice. Timing matters less than a workable eating and training pattern. More grams of protein do not promote more muscle growth when total intake is adequate.
Weight gainer: calorie and protein considerations
A mass gainer combines carbohydrate and protein, sometimes with fat, creatine, vitamins or herbs. It can be convenient when an APD identifies a suitable energy surplus and food volume is limiting. The Australian Institute of Sport classifies mixed macronutrient products as sports foods for specific situations within a broader plan.[5]
Compare nutrients and calories per serving, not a front-label number. Multi-scoop serves can be difficult to tolerate and displace food. Seek a clear ingredient list, manageable portion, suitable macronutrients, allergen disclosure and no unnecessary proprietary blend.
Homemade smoothies or protein shakes can be flexible, not guaranteed shortcuts. A planned drink can support weight gain when appetite is limiting. Clinician-selected nutritional supplements differ from bodybuilding powders; consult a health professional before using them as meal replacements.
Creatine, body composition and muscle mass
Creatine monohydrate increases muscle creatine availability. A 2024 meta-analysis found a small additional average lean-mass increase when adults under 50 combined creatine with resistance training.[6] It may support muscle performance in that setting. Early short-term weight gain can include intracellular water, not pure new muscle mass.
Creatine does not treat being underweight. Suitability depends on health, medicines, training and competition rules. Seek advice with kidney disease, pregnancy, complex care or concerning symptoms. It can raise measured creatinine, which needs context during kidney-test interpretation. No loading phase or public dose is prescribed here.
Supplement safety and weight management
Australian sports products may be foods or therapeutic goods depending on presentation, ingredients and claims. The TGA says relevant therapeutic goods require ARTG entry before supply or advertising.[7] An AUST L or AUST R number is not proof that a product best fits your goal.
Competitive athletes face contamination risk. Of 200 non-batch-tested sports supplements bought online for a Sport Integrity Australia survey, 35% contained WADA-prohibited substances; 57% of positive products did not list them.[8] Use the Sport Integrity App and match the exact batch. Testing reduces, but cannot eliminate, risk.
Many supplements contain overlapping creatine, caffeine, vitamins or minerals. Do not stack products automatically. Stop and seek advice for allergy, persistent vomiting or diarrhoea, severe pain, swelling, palpitations or other concerning symptoms.
Weight gain questions
What is the best supplement for weight gain?
There is no universal best supplement, and no option reliably promotes weight gain by itself. For healthy adults who want to gain weight and build muscle, extra protein may fill an intake gap and creatine has evidence for small additional lean-mass gains with training. For illness-related loss or malnutrition, the best option may be an individually selected oral nutrition supplement, or no retail supplement until the cause is assessed.
How can skinny people gain weight safely?
Start by checking whether weight is stable and whether there are symptoms or restrictive eating patterns. Build a food-first plan with regular nutrient-dense meals and snacks, then add progressive exercise if medically appropriate. A GP or APD can set a realistic goal without relying on the stigmatising label “skinny”.
What can help you gain weight faster?
Trying to increase weight fast can favour body fat or fluid gain, worsen symptoms and obscure an underlying condition. Consistency, enough energy and protein, sleep, recovery and progressive training matter more than a rapid promise. Severe undernutrition requires supervised restoration because of refeeding risk.
Can I gain weight in two weeks?
The scale can change in two weeks, but it cannot show how much is muscle. Water, glycogen and digestive contents change quickly, while muscle development is slower. Judge progress by a clinician-defined goal, strength, function, symptoms and dietary adequacy, not only scale speed.
Do I need supplements to gain weight?
Often, no. Many people can raise their weight through ordinary food when the plan matches their needs. Supplements help only when they solve a documented problem such as limited appetite, food volume, convenience or an assessed protein gap and do not delay medical care.
References
- Better Health Channel. Weight and muscle gain. Checked 19 July 2026.
- Healthdirect Australia. Malnutrition. Checked 19 July 2026.
- Matthews-Rensch K, et al. The Australasian Society of Parenteral and Enteral Nutrition: consensus statements on refeeding syndrome. Nutrition & Dietetics. 2025. doi:10.1111/1747-0080.70003. PubMed
- Morton RW, et al. A systematic review, meta-analysis and meta-regression of protein supplementation with resistance training. British Journal of Sports Medicine. 2018;52:376–384. doi:10.1136/bjsports-2017-097608. PubMed
- Australian Institute of Sport. Group A supplements and sports foods. Checked 19 July 2026.
- Burke R, et al. The effect of creatine supplementation on resistance training-based changes to body composition: a systematic review and meta-analysis. Journal of Strength and Conditioning Research. 2024;38:1813–1821. doi:10.1519/JSC.0000000000004862. PubMed
- Therapeutic Goods Administration. Importing or supplying sport supplements. Checked 19 July 2026.
- Sport Integrity Australia. New supplement survey finds one in three products contain banned substances. 9 April 2025.
Evidence checked: 19 July 2026. General information only; it does not replace care from a GP, Accredited Practising Dietitian, sports physician, pharmacist or eating-disorder clinician.
