Updated October 29, 2014.

While much of the country scrambles to fight obesity, some people are just trying to gain weight, and they want to do it in a healthy way. Sure, you can eat like Michael Phelps, consuming several thousand calories a day (you’d better be exercising too!), but that’s not necessarily a healthy approach for the average person.

And, if you have a food allergy, you may have a hard time keeping weight on, especially if you have to follow a severely restricted diet related to multiple food allergies.

Kids are particularly susceptible to poor weight gain and growth when they suffer from a milk allergy or from multiple food allergies.

Here are five super simple ways to put the weight on slowly but surely, and in a healthy manner:

Increase your portion sizes. Yes, simply said, eat more food. Go for second helpings, add an extra spoonful, and fill your plate. Eating more food naturally ups the total calories. Warning: eat more of everything, not just the fatty fried or sugary sweet foods. Although these foods will contribute to weight gain, they won’t add to your health.

Eat more frequently. Squeezing in another meal or snack will increase your caloric intake by hundreds of calories. If you eat three meals and one snack, add another snack. If you’re a meal skipper, such as in breakfast, make sure you add it back in. Optimally, if you can manage to eat three meals and two to three snacks each day, you’ll increase you’re overall calorie and nutrient delivery. Reminder: make your food choices mostly healthy and allergen-free.

Eat something before bedtime. A pre-bedtime snack will give your body calories at a time when they won’t be burned off, which will increase your chances for weight gain. Some good options are a smoothie (check out this milk-free smoothie recipe here), a small bowl of cereal, or some nut-free butter on toast.

Pad and add the fat. Fat, like butter, oils and avocado, are concentrated sources of calories, weighing in at 9 calories per gram (compared to 4 calories per gram for protein and carbohydrate), and can quickly increase calories in any food item. Try smoothing avocado on a lunchmeat sandwich, toss veggies in butter or olive oil, and double-dress pasta with olive oil first, then sauce. Don’t forget an extra slice of cheese, an extra tablespoon of nut-free butter, or a small bowl of olive oil for bread dipping. To keep it healthy, opt for the healthy fats—mono-unsaturated and poly-unsaturated fats—like plant-based oils (canola, sunflower, safflower, olive oil for example), nuts, fish, and seeds, if these foods fit within your dietary limitations.

Choose nutrient-dense foods. Always, always, always go for healthy foods first, over the unhealthy choices. You’ll guarantee a punch of nutrition—nutrients your body needs to be healthy—while getting those extra calories you want.  Some foods that will work towards your overall health are: fruit, veggies, whole grains, protein sources, dairy or non-dairy substitutes, and healthy fats. For those foods that are high in nutrients but low in calories, like fruit and veggies, try to pair them with other high calorie foods to bump up the calories. For example, pair fruit with a yogurt dip, toss veggies in oil or butter or include a dip like hummus.

Of course, you can always have a daily dessert, or that delicious allergen-free cookie, but don't rely too heavily on these kinds of foods. One a day won't derail your efforts to be healthy, but more than that puts the "healthy" you're striving for, at risk.

Gaining weight in a healthful manner isn’t difficult-- it just requires some forethought and planning on your part. Be mindful of boosting your caloric intake each time you sit to eat, and plan your daily approach to eating so that is supports your weight gain goal.

What techniques for weight gain work for you?

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