Healthy weight gain is not about eating as much as possible or relying on mass-gainer products. The goal is to increase body weight gradually while supporting muscle, bone and overall nutrition.
If you are underweight or have lost weight without trying, it is important to consider why before simply adding calories. Unintentional weight loss can be a sign of an underlying medical, gastrointestinal, thyroid, mental-health or medication-related problem.
Start with a gradual calorie increase
The NHS suggests that adults trying to gain weight can start by adding roughly 300–500 calories per day and adjust based on progress. This is a practical starting range rather than a universal prescription.
A modest surplus makes it easier to gain gradually instead of using aggressive “bulk” strategies that mainly add body fat.
Choose calorie-dense foods that also add nutrition
Useful options include:
- nuts, seeds and nut butters;
- olive oil, avocado and other unsaturated fats;
- whole grains, rice, oats, potatoes and pasta;
- milk, yogurt, cheese or fortified alternatives;
- eggs, fish, poultry, lean meat, tofu, tempeh, beans and lentils;
- dried fruit and smoothies made with nutrient-dense ingredients.
Adding olive oil, nuts, seeds, cheese, yogurt or nut butter to foods you already eat can raise calories without requiring very large portions.
Eat more often if large meals are difficult
Three meals plus one or two snacks can work well, but there is no mandatory meal frequency. Smaller, more frequent meals are often easier for people with a low appetite.
Prioritize protein—but do not overdo it
Protein helps support muscle when paired with resistance training. For healthy adults who strength train, around 1.6 g/kg/day is a practical evidence-based target for maximizing the average muscle-building response; going substantially higher does not consistently add more lean mass.
See our guide: Protein for Muscle Growth and Healthy Aging.
Use strength training to direct some of the gain toward muscle
Resistance training gives the body a reason to build and retain muscle. A beginner does not need an advanced bodybuilding split. Two or more full-body strength sessions per week can be an effective starting point.
See our Beginner Weight Training Program.
What about shakes?
A homemade smoothie or commercial oral nutrition drink can be useful when appetite is poor or food intake is difficult. But a “mass gainer” is not automatically better than food. Many are simply concentrated calories from carbohydrate and protein.
If using a packaged product, check the ingredient list, serving size, protein amount, added sugar and whether the product has credible third-party testing. Avoid products that promise hormone manipulation, steroid-like effects or extreme muscle gain.
Do not rely on junk food to gain weight
Chocolate, fried foods, sugary drinks and highly processed snacks can add calories, but building a weight-gain plan around them can worsen diet quality. Aim to increase calories while still getting adequate protein, fiber, vitamins, minerals and healthy fats.
When should you see a healthcare professional?
Seek medical advice if you:
- have lost weight unexpectedly;
- continue losing weight despite trying to eat more;
- have persistent diarrhea, vomiting, difficulty swallowing or abdominal symptoms;
- have symptoms of thyroid disease, diabetes or another medical condition;
- have very low appetite, depression, anxiety around food or possible eating-disorder symptoms;
- are frail, older, pregnant, or have kidney, liver or other chronic disease requiring individualized nutrition.
Bottom line
For most healthy adults who genuinely need to gain weight, the safest approach is gradual: add roughly 300–500 calories per day, eat nutrient-dense foods, include adequate protein and use resistance training. Sudden or unexplained weight loss should be assessed rather than self-treated with supplements.
Sources
- NHS: Healthy ways to gain weight
- American College of Sports Medicine: 2026 Resistance Training Guidelines
- Protein supplementation and resistance training meta-analysis
Medical note: Weight goals and calorie needs can differ substantially with age, pregnancy, illness, kidney disease, eating disorders and other health conditions.
