If you’re always on-the-go, meal replacement shakes are practical. They get extra brownie points for being portable and convenient. Ideally, they would make an easy meal or snack when the other option is a hanger-induced run to the nearest drive-through, or even worse, just going hungry. Simply add water (or milk) and it’ll shush any loud, growling stomach. Then there’s the added advantage of taking the guesswork out of planning and preparing healthier meals; or in the case of Soylent, being a quick meal when just eating is simply a hassle.

As part of a weight loss regimen, shakes can be helpful, if drinking it means you’re not eating junk calories elsewhere. So, if you swap out your typical breakfast of a blueberry muffin chased with a vanilla soy latte (a potential difference of 300-600 calories), then you’ll be eating fewer calories overall. Do this enough to be consistently in a calorie deficit, and you’re well on your way to weight loss! That’s all it is.

There’s nothing magical about meal replacement shakes themselves for weight loss, except for the fact that they tend to have a thicker consistency, which helps suppress hunger. In shakes with a higher fat content like Soylent, the fat can help you feel fuller for longer because they leave the stomach more slowly. Overall, it’s still all a matter of controlling how many calories you eat though. If you’re drinking shakes in addition to staying on your regular eating habits, you can bet the scale will rebel against your wishes.

However, that does mean these are perfect for people with the opposite problem who have trouble gaining weight. For these folks, they typically lack the appetite to eat the required amount of calories for weight gain, so shakes (and any additional source of calories, really) can be a no-fuss way to get more calories without making them feel too uncomfortable and bloated.

Overall, meal replacement shakes like Shakeology have their place and can be useful for lifestyles that constantly call for quick and convenient meals, but they can quite literally come at a high cost. In reality, we could all use a reminder that meal replacement shakes are just like any other supplement: use them if you need the extra boost in calories in your day.