What Foods Can You Eat to Gain Weight?

Calorie-dense whole foods, especially those rich in protein and healthy fats, are the most effective choices for gaining weight in a healthy way. Nuts, nut butters, whole milk, eggs, avocados, olive oil, fatty fish, whole grains, and dried fruits all pack a lot of energy into relatively small portions, making it easier to eat more without feeling uncomfortably stuffed. But what you eat matters beyond just calories: research consistently shows that the proportion of protein in your diet determines whether extra weight ends up as muscle or mostly fat.

Why Protein Shapes the Kind of Weight You Gain

Eating more calories than you burn will cause weight gain, but protein content has a dramatic effect on where those extra calories go. In a controlled overfeeding trial, people eating a low-protein diet actually lost lean body mass even while gaining fat, whereas those on normal or high-protein diets gained roughly 3 kg of lean mass alongside the fat gain. Fat gain itself was similar across all groups regardless of protein intake.¹ In other words, if you eat a surplus of calories but skimp on protein, your body stores fat while breaking down muscle. That is the opposite of what most people trying to gain weight actually want.

A large meta-analysis looking at protein intake and lean mass found that younger adults gained the most lean body mass when eating about 1.6 grams of protein per kilogram of body weight per day or higher, while older adults saw benefits at somewhat lower intakes.² For someone who weighs 70 kg (about 154 pounds), that translates to roughly 112 grams of protein daily. You do not need to obsess over hitting an exact number, but the broad takeaway is clear: if you are trying to gain weight, protein is not optional. It is the single biggest dietary lever for tipping the balance toward muscle rather than fat.

High-Calorie Whole Foods That Make Gaining Easier

The practical challenge for many underweight people is not knowing which foods are calorie-dense, but actually getting enough of them down. Appetite can be a real bottleneck, so foods that deliver a lot of energy per bite or per spoonful are your best friends. Here are categories that consistently stand out:

• Nuts and nut butters: Almonds, cashews, peanuts, and walnuts range from about 550 to 650 calories per 100 grams. A couple of tablespoons of peanut butter on toast adds close to 200 calories with minimal effort. Nuts also provide a mix of protein, fat, and carbohydrates, though the exact balance varies.
• Oils and fats: Olive oil, coconut oil, and butter deliver about 120 calories per tablespoon. Drizzling olive oil over vegetables, rice, or pasta is one of the easiest ways to add calories to meals you are already eating without increasing the volume of food on your plate.
• Whole milk and full-fat dairy: A glass of whole milk provides about 150 calories along with protein, fat, and calcium. Cheese, full-fat yogurt, and cream are similarly dense.
• Avocados: A single medium avocado contains around 240 calories, mostly from monounsaturated fat, and blends easily into smoothies or spreads.
• Dried fruits: Dates, raisins, and dried apricots concentrate the sugars and calories of fresh fruit into a much smaller package. A handful of dates can deliver 200 or more calories.
• Starchy foods: Rice, potatoes, sweet potatoes, oats, and whole-grain bread provide sustained energy from carbohydrates and are easy to eat in large portions.
• Fatty fish and red meat: Salmon, mackerel, and lean cuts of beef or lamb combine protein with fat, helping you hit both calorie and protein goals simultaneously.

Nuts deserve special mention because their calorie density can be deceptive. Research on nut consumption and body weight has found that people who eat nuts regularly do not necessarily gain as much weight as the calorie math would predict, likely because nuts are quite satiating and not all of their energy is fully absorbed during digestion.³ This is actually good news in general nutrition, but if your goal is gaining weight, it means you may need to eat nuts more deliberately, for instance as part of a trail mix with dried fruit and chocolate, rather than relying on them as your sole calorie booster.

Should You Use Ultra-Processed Foods to Gain Weight?

It might seem logical to reach for ice cream, fast food, and packaged snacks when you need extra calories. Ultra-processed foods are engineered to be easy to overeat, and research confirms this works. In a tightly controlled study where people were given unlimited access to either ultra-processed or unprocessed meals matched for available calories, protein, fat, sugar, and fiber, those eating ultra-processed food consumed about 500 extra calories per day and gained roughly 0.9 kg over two weeks. The same people, switched to unprocessed food, spontaneously ate less and lost about the same amount of weight.⁴

So ultra-processed foods are undeniably effective at driving calorie intake up. The problem is what kind of weight you gain. The extra calories from ultra-processed diets in that study came almost entirely from additional carbohydrate and fat, not protein. Without adequate protein, extra calories preferentially become body fat rather than muscle. There is also the longer-term concern: a diet built around ultra-processed food may cause you to overshoot your goal weight, develop metabolic issues, or crowd out the micronutrients your body needs to function well. Using some processed foods strategically, say a bowl of granola or a protein bar when you cannot stomach a full meal, is perfectly reasonable. Building your entire weight-gain plan around chips and fast food is a strategy with obvious downsides.

Why Gaining Weight Feels Harder Than It Should

People who struggle to gain weight often feel like their body is fighting them, and physiologically, that is exactly what is happening. Your body has internal defenses against sustained overfeeding. Classic overfeeding experiments showed that when lean individuals were deliberately overfed, their appetite decreased and their energy expenditure increased compared to people of the same weight who had not been overfed. The body essentially turns up the thermostat and dials down hunger signals, pushing back toward the original weight.⁵

This is why gaining weight can require a sustained, conscious effort rather than just casually eating a bit more. Your body adapts to calorie surpluses by burning more energy and making you feel less hungry. Some people have stronger versions of this response than others, which partly explains why certain individuals stay lean no matter what they eat while others gain weight more easily. The practical implication is that weight-gain diets need to be consistent over weeks and months, not just a few days of extra snacking.

Eating More Often and Drinking Your Calories

If you struggle with large meals, eating more frequently is one of the most consistently effective strategies. Research on meal timing and calorie intake in healthy adults found that eating more frequently throughout the day predicted higher total calorie consumption.⁶ Rather than trying to force yourself through three enormous meals, spreading your intake across five or six smaller ones, including snacks between meals, takes the pressure off any single eating occasion.

Liquid calories are another workaround for limited appetite. Smoothies blended with whole milk, nut butter, banana, oats, and protein powder can easily reach 600 to 800 calories in a single glass, and most people find it far easier to drink those calories than to eat the equivalent as solid food. Whole milk on its own is already a reasonable calorie source, and research has found that milk consumption after exercise acutely increases muscle protein synthesis, with longer-term studies showing greater lean mass gains when milk is combined with resistance training over at least 12 weeks.⁷ Homemade smoothies, milkshakes, and even savory options like blended soups with cream or coconut milk are all effective vehicles for extra energy.

Combining Food With Resistance Training

Eating more without exercising will make you gain weight, but most of it will be fat. If you want to shift the ratio toward muscle, resistance training is essential alongside a calorie surplus. A study in bodybuilders compared a larger calorie surplus to a smaller one during a resistance-training program and found that both groups gained muscle, but the group eating more gained significantly more body fat as well.⁸ The group with the larger surplus did see somewhat more muscle growth, but the tradeoff was more fat gain too.

Separate research in resistance-trained individuals found strong evidence that changes in body mass predicted changes in skinfold thickness, meaning much of the weight gained during a calorie surplus ended up as subcutaneous fat even in trained people.⁹ The practical lesson is that a moderate surplus paired with consistent strength training is more efficient than a massive surplus. Eating 300 to 500 calories above your maintenance needs, with adequate protein, gives your body enough raw material to build muscle without accumulating unnecessary fat. Larger surpluses do not proportionally increase muscle gain; they mostly just add more fat on top.

It is also worth noting that the food-exercise interaction has limits. An 18-month trial in middle-aged and older men found that adding fortified milk to a resistance training program did not enhance muscle size, strength, or function beyond the exercise alone in participants who already had adequate nutrition.¹⁰ If your overall diet is already meeting your protein and calorie needs, piling on extra calories from any single food probably will not accelerate muscle growth further. The benefit of eating more comes primarily when your baseline diet is insufficient.

When Appetite Itself Is the Problem

Some people trying to gain weight are not just making poor food choices; they genuinely lack the appetite to eat enough. Chronic low appetite can have many causes, from stress and medication side effects to underlying medical conditions, and addressing those root causes is important. One underappreciated nutritional factor is zinc status. Research in animals has shown that zinc stimulates food intake rapidly by acting through appetite-regulating pathways linked to the vagus nerve, and that even early-stage zinc deficiency can suppress hunger.¹¹

In humans, a study of undernourished children found that those with low serum zinc levels experienced significant increases in appetite and growth after 24 weeks of zinc supplementation.¹² This does not mean that everyone with a small appetite should start popping zinc supplements. But if you have been eating poorly for a while or have a restricted diet, marginal zinc deficiency is plausible, and zinc-rich foods like red meat, shellfish, pumpkin seeds, and legumes are worth incorporating. If poor appetite persists despite dietary changes, a doctor can check zinc levels and other possible causes.

Your Gut Bacteria Affect How Many Calories You Actually Absorb

Two people eating the same meal can absorb meaningfully different amounts of energy from it, and your gut microbiome is one reason why. Research has established that the gut microbiome influences nutrient metabolism and energy expenditure.¹³ The mechanisms include changes in how efficiently energy is extracted from food, modulation of fat metabolism, and effects on hormones that regulate hunger and satiety.¹⁴

Recent precision-nutrition work has quantified just how much variation exists. On a high-fiber, whole-foods diet, the efficiency of energy absorption ranged from 84% to 96% between individuals, meaning some people lost substantially more calories in their stool than others. Three factors drove this variation: the amount of microbial biomass in the gut, how actively those microbes were fermenting food, and how quickly food moved through the colon.¹⁵ On a low-fiber diet, this between-person variation largely disappeared because the microbes had less substrate to work with.

For someone trying to gain weight, this has a couple of practical implications. First, if you are eating a very high-fiber diet, you may not be absorbing as many calories as you think. You do not need to abandon fiber, but being aware that a plate of lentils and vegetables may deliver fewer usable calories than the nutrition label suggests can help you calibrate. Second, if two people eat the same weight-gain diet and one gains faster, differences in gut bacteria are a plausible explanation beyond just genetics and activity levels. The science is not yet at the point where you can test your microbiome and get a personalized calorie-absorption number, but the research makes clear that absorption efficiency is not a fixed value.

The Cost of Gaining Weight on Whole Foods

Advice to “eat more whole foods” runs into a real-world barrier: cost. Research tracking food prices has consistently found that minimally processed foods have far higher nutrient density but are also substantially more expensive per calorie than ultra-processed alternatives. During periods of economic disruption, this affordability gap widens, pushing people toward cheaper, energy-dense processed options.¹⁶ That said, research on nutrient density and cost has also shown that while fruits and vegetables are an expensive source of raw calories, they provide key nutrients at a reasonable cost per serving.¹⁷

If budget is a constraint, some of the most cost-effective weight-gain foods are also among the most calorie-dense whole foods: peanut butter, whole milk, eggs, rice, oats, bananas, and canned beans. These staples deliver both protein and energy without breaking the bank. Olive oil, while not the cheapest fat, is relatively economical per calorie compared to many other whole foods. Buying nuts and dried fruits in bulk, choosing frozen vegetables over fresh, and cooking grains in large batches are all strategies that bring the cost of a whole-food weight-gain diet closer to what you would spend on processed alternatives. The key insight is that gaining weight on whole foods does not require expensive superfoods or specialty products. It requires large, consistent portions of affordable staples, eaten frequently enough to overcome the appetite suppression your body naturally produces in response to a calorie surplus.