When the warm weather starts to kick in, we’re drawn to the patio for some rest, relaxation and a few cold beverages. But it only takes a couple of drinks to derail even the healthiest of diets.

If you’re wondering how just a few cans of pop and a couple of IPAs can sneak into your otherwise healthy routine and wreak havoc on your diet, you wouldn’t be alone. Liquid calories are one of the most insidious culprits in everyone’s diet during BBQ season, here’s why:

Liquid calories like juice and pop don’t have strong satiety properties, which means they don’t suppress your appetite. Although they add up in a big way throughout the course of a day, they don’t actually make you feel full for a long period of time.

Most people have a hard time cognitively associating liquids with calories, or even the feeling of fullness and satisfaction. When we don’t feel full, we continue consuming calories until we achieve a feeling of contentment—and when it comes to liquids, that could take a long time.

Liquid calories are often quicker and easier to consume than solid calories. It’s easier to grab a pop then it is to sit and eat a salad, which is why you’ll find people downing two or three drinks in the time it takes to eat a balanced meal.

Just because some beverages have more calories than a piece of fruit or some granola doesn’t mean that they will be more filling than solid food. Nutritionally dense foods take a much longer time to break down and therefore keep us fuller longer. Liquids like juice or alcohol have more calories than a banana, but a banana has more nutritional density for our bodies to break down and use as energy.

The stretching of your stomach and intestines is what signals your brain to feel full or satiated. Since fluids like smoothies or juice don’t stretch these organs as much as solid food would, you’re likely to consume more calories for a longer period of time to achieve that feeling of fullness.

“Healthy” beverages can have as much, if not more sugar than pop. This is especially true for smoothies sold at fast food restaurants and marketed as a healthy alternative to fountain pop. These smoothies don’t have the nutritional value of homemade smoothies and are usually filled with sugar-laden yogurt and fruit purees. This doesn’t mean that you should swear off smoothies forever, it just means that you should try to stick to homemade blends that you can pack with protein powder, greens and real fruit.

Although there’s a place for liquid calories in a healthy and well-rounded diet, it’s important to be aware of the nutritional density associated with the liquids you’re knocking back. If you’re sipping away on two or three sugary beverages per day, you’re definitely not doing your body any favours.

That being said, there is one fluid you can never have too much of—water. When in doubt, substitute a fizzy pop for some carbonated water, or add some fruit to your water bottle to keep things interesting. If you’re someone who needs a drink in hand, opt for some sugar-free, calorie-free aqua and keep your healthy lifestyle on track.