Do smoothies really help you lose weight?

They can be used as a meal replacement. However, this is only for smoothies that you make yourself. Commercial bought smoothies contain a lot of sugar.

that totally depends on if you are consuming less total calories per day if you are drinking smoothies.
Mushed up food in liquid form has no special diet magic attatched to it.
Its all about calories.
Eating fewer calories than you burn and you will lose weight.
Eating MORE calories than you burn and you will gain weight.

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Use less salt in food

It depends on several factors. What is going in the smoothie? How many are you drinking in a day? What else are you eating the rest of the day? If the smoothie is, say, replacing a conventional breakfast, you're probably going to be fine.

No liquid food is often a method used if looking to gain weight by increasing calorie intake.

If anything smoothies would make you hungrier, especially seeing as they are mainly fructose

Depends on what's in them and how many you drink. Most of the smoothies and recipes for smoothies I've seen tend to be very, very high in sugar. That's not good.

Losing weight is a process of eating a balanced diet, taking in fewer calories than you expend and getting some exercise. Remember, though, that all calories are not the same. Foods high in carbs (energy) turn to fat if you don't burn up that energy. Potatoes, white rice, pasta...to name a few.

Depends on the smoothie and depends on whether or not you're replacing bad calories with good calories. You still have to have enough calories-not too much and not too few.