Bringing up a healthy, chubby-cheeked baby is every new parent’s dream, but finding the right milk for optimal weight gain without causing gas can be challenging. While all infant formulas are designed to support healthy growth, some babies have more sensitive tummies.
Studies show that between 2% and 15% of infants may experience some intolerance to formula ingredients. At the same time, fussiness and gas are very common in young babies and are often not caused by the formula itself.
In this article, we’ll explain how different formulas affect weight gain and gassiness. We’ll also highlight some of the best infant milks that help babies gain weight comfortably, and give you tips to keep your little one’s stomach content.
Does Every Formula Help a Baby Gain Weight?
Generally, yes – almost any standard formula will help your baby gain weight appropriately. It is similar in calories to breast milk, providing about 20 calories per ounce and 0.45 grams of protein. This means if your baby consumes enough formula, they should gain weight at a healthy pace.
Research has even found that formula-fed infants tend to gain weight a bit faster than breastfed infants, mainly due to higher protein content in formula. So, as long as your baby is feeding well on a formula, it’s doing its basic job of nourishing and helping your baby grow.
That said, not all formulas are identical. There are specialty formulas designed for babies with specific needs or conditions. For example, premature babies or infants diagnosed with “failure to thrive” might require fortified formulas with extra calories and minerals to meet the needs of these infants.
The Difference Between Regular Milk and Fortified Milk for Weight Gain
It’s important to clarify what we mean by “regular” vs. “fortified” milk. For infants under 1 year, “regular milk” does NOT mean plain cow’s milk. (In fact, pediatricians do not recommend straight cow’s milk for infants under 12 months, because it lacks the proper nutrient balance and can cause digestive issues.) Here, regular milk refers to standard infant formula or normal breast milk, which have ~20 cal/oz as mentioned. Fortified milk refers to milk that has been enhanced with extra nutrients or calories for babies who need additional support gaining weight.
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Standard infant formulas
are iron-fortified and nutritionally complete for most babies. They contain the right balance of protein, carbs, fats, vitamins and minerals to mimic breast milk’s nutrition. These are usually enough to ensure steady weight gain in healthy, full-term infants. If your baby is drinking the recommended amount and growing along their curve, a regular formula is doing its job.
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Fortified formulas or high-calorie feeds
on the other hand, come into play if a baby isn’t gaining adequately. For example, preterm infants often get special formulas with extra calories and protein to “catch up” growth. In some cases, doctors may instruct parents to concentrate formula (e.g. using more powder per ounce of water) to increase calories per feeding. These fortified feeds can bump up calories to 22, 24, or even 27 cal/oz. The key difference is that fortified milk provides more calories in the same volume, promoting faster weight gain – but this approach is only used when medically necessary. For a typical baby, standard formula or breast milk is sufficient and actually safer for their digestion.
What Is the Relationship Between Milk and Gas in Infants?
It’s very common for babies to be gassy during the first few months of life. That’s because their digestive systems are still developing. As they learn how to eat and digest, babies naturally swallow air and produce gas while breaking down milk whether it’s formula or breast milk.
What’s normal:
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Most newborns grunt, squirm, turn red, or even cry due to gas, but this is usually harmless.
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As long as your baby is:
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Feeding well
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gaining weight adequately
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passing soft mushy stools that are green, yellow or brown (but NOT bloody, white or black)
then gas alone is not a sign of a serious problem or formula intolerance.
What causes gas?
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Air swallowing: Babies often swallow air when bottle feeding especially if the nipple flow is too fast or if they’re crying before feeding.
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Digestion: Milk itself (breast or formula) can ferment slightly in the intestines due to gut bacteria, creating normal gas.
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Feeding behavior: Fast feeding, gulping, or crying while eating can increase swallowed air and lead to more gas.
When to worry?
If gas leads to significant discomfort, poor weight gain, projectile vomiting, or constant fussiness, speak with your pediatrician. These could be signs of formula intolerance or sensitivity.
In some cases, specific ingredients in formula can worsen gas for sensitive babies. Let’s explore those ingredients next.
Ingredients That Cause Bloating and Should Be Avoided
Most standard formulas use similar core ingredients: a protein (from cow’s milk or soy), a carbohydrate source (like lactose, the milk sugar), and fats (vegetable oils). These are generally well-tolerated.
However, a minority of babies might have trouble with one of these components:
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Lactose:
This natural milk sugar is the main carb in both breast milk and most formulas. True lactose intolerance in infants under 1 is exceedingly rare. But if a baby lacks enough of the enzyme lactase, lactose can go undigested and ferment in the gut, causing gas, bloating, and diarrhea.
In such cases (often temporary or due to a stomach bug), a low-lactose or lactose-free formula may help ease bloating. Signs of possible lactose overload include very gassy, watery stools and discomfort after feedings. Always check with the doctor, since these symptoms can have other causes too. Remember, lactose intolerance is uncommon in young infants, so don’t eliminate lactose unless a pediatrician suspects it.
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Intact Cow’s Milk Protein:
The protein in standard formula comes from cow’s milk (usually a mix of casein and whey). Some babies have difficulty digesting the full-size milk proteins. An immature digestive system can struggle to break down these proteins, leading to gas and fussiness.
In more severe cases, the baby might have a cow’s milk protein allergy, which causes symptoms like:
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excessive crying
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Vomiting
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blood in stool
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skin rashes
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diarrhea
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breathing issues
If your baby’s gas is accompanied by other allergy signs, talk to a doctor.
For general protein sensitivity, switching to a formula with partially hydrolyzed protein (proteins broken into smaller pieces) can make a huge difference. These “gentle” or “comfort” formulas are easier to digest and produce less gas. For true milk protein allergy, a fully hypoallergenic formula (with extensively broken-down amino acids) may be needed.
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Certain Additives or Extras:
In an effort to address common issues, some formulas include additional ingredients that could bloat a baby. For example, formulas for reflux are thickened with starch or gum (like rice starch or carob bean gum) to help milk stay down. These are very useful for spit-up, but in a baby without reflux they might cause the tummy to feel overly full or produce more gas due to the heavier consistency.
Some other formulas add prebiotic fibers (GOS/FOS, similar to breast milk oligosaccharides) to promote gut health. While generally beneficial, these can sometimes make babies a bit gassier as the fibers ferment – usually a mild effect.
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Soy Protein:
Just like with milk protein, some babies are allergic to the proteins in soy-based formulas. Soy protein intolerance can manifest as symptoms like:
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upset stomach
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skin reactions
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respiratory problems
If your baby is reacting to their soy formula, you might need a specialized option that avoids both milk and soy protein, such as a hypoallergenic or amino acid-based formula.
The Best Types of Milk That Gain Weight Without Gas
If your baby is one of those with a sensitive tummy, you’ll want a formula that still provides all the nutrition for weight gain minus the gassy side effects.
Fortunately, several formulas are formulated specifically for easy digestion and comfort while ensuring healthy growth. We’ll look at two most popular options often recommended by doctors and experienced parents alike:
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Nan AR
Nan AR by Nestlé is a specialized formula designed to help manage frequent spit-up and mild reflux. The "AR" stands for "Anti-Regurgitation," and the formula is slightly thickened using starch to help keep feeds down more effectively.
Key benefits include:
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Thickened texture that reduces reflux without compromising digestibility.
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Gentle protein blend, modeled after breast milk, to support easier digestion.
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Includes DHA and ARA, essential fatty acids that support brain and eye development.
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Probiotics and 2’-FL, components that promote gut health and immune support.
Nan AR is often recommended for babies who are gaining weight slowly due to frequent spit-up, but who otherwise tolerate milk proteins well. It offers a gentle, balanced formula that supports both comfort and growth — making it a strong option for infants needing help with reflux without the digestive upset that can come with heavier feeds
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Aptamil AR
Aptamil AR is a thickened anti-reflux formula developed by Danone, designed to reduce frequent spit-up in infants while still offering complete and gentle nutrition. It's enriched with ingredients that support digestion and comfort, making it suitable for babies with reflux who still need balanced growth support.
Key benefits include:
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Thickened formula with carob bean gum to help reduce regurgitation and keep feeds down.
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Contains DHA and ARA to support healthy brain and eye development.
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GOS/FOS prebiotic blend (9:1 ratio), clinically shown to support a healthy gut microbiome.
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Fortified with iron and free from added sucrose.
Aptamil AR is ideal for babies who experience frequent spit-up or mild reflux but do not show signs of a milk allergy. It helps ease digestive discomfort while providing essential nutrients for steady weight gain. Pediatricians often recommend it as a gentle, effective option for reflux without switching to hypoallergenic formulas unnecessarily.
Tips to Ensure a Comfortable Stomach for Your Baby with Healthy Weight Gain
Feeding technique and general care can be just as important as the choice of milk when it comes to preventing gas and helping your baby gain weight happily. Here are some parent and doctor-approved tips to keep your little one’s tummy comfortable:
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Burp Frequently and Properly:
Burping helps release air bubbles that your baby swallows during feeds. Don’t wait until the end of a feeding, pause halfway through the bottle to burp your baby, then continue feeding. If your baby is very gassy, consider burping after each ounce or two of formula.
Use an effective burping position:
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Over the shoulder: Position your baby vertically with their head just above your shoulder. Make sure to support their little noggin with your shoulder or hand. Gently pat or rub their back.
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Armrest: Sit your baby on your lap, facing sideways. Lean them to a slight forward incline, with their upper body resting on your forearm. Softly cradle their jaw in your hand — being careful to keep your hand away from their throat. Gently pat or rub their back.
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Use the Right Bottle:
Bottle design plays a big role in how much air your little one swallows as they feed. For the best results, use an angle-neck bottle with a slow-flow nipple. Vented wands with internal straws are a great option, as are bottles that use pre-sterilized disposable drop-in liners.
Also be mindful that — if you’re formula feeding — the way you prepare the baby's bottle can make a difference, too. Instead of shaking the bottle to incorporate the formula (which turns baby’s food into an air bubble factory) stir or swirl it in. Then, wait a couple of minutes for the air bubbles that are there to rise to the top.
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Feed Before Baby Gets Too Hungry:
Don’t let your baby get extremely hungry and crying hard before feeding. When babies cry intensely from hunger, they gulp in the air. Then when they finally eat, they tend to guzzle quickly (again swallowing air). The result? A gassy tummy. To avoid this, watch for early hunger cues (stirring, sucking on hand, rooting) and feed promptly. A calmer baby will eat more slowly and swallow less air, aiding digestion and weight gain.
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Optimal Feeding Position:
Keep your baby’s head higher than their stomach during feedings. An upright or semi-upright position (rather than flat on their back) helps milk move down smoothly and air rise up, making burping easier. If bottle-feeding, hold the baby at a slight incline. After feeding, hold baby upright for a few minutes to let gravity assist in clearing any air bubbles before you lay them down.
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Tummy Time and Gentle Movement:
Give your baby tummy time each day (while awake) and gentle exercises to help push out gas. Laying them on their tummy can put mild pressure on the belly, helping to release gas from the bottom end.
You can also do the “bicycle” with their legs (lay baby on their back and pedal their legs gently) to help work out trapped farts. Many babies find relief from these motions, and it can be a fun playtime routine. Just make sure to wait at least 20-30 minutes after feeding before any tummy-down positions to avoid spit-up.
