When we are judging the merits of what someone is saying, one thing we might say, when it's just a bunch of baloney, is:

Tutto fumo, niente arrosto.

Literally, this means, "all smoke, no roast." A roast refers to meat, so there is also no meat on the bones, although that is a different metaphor. 

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There are various ways to express this in English, for example:

All talk and no action.
All talk and no walk.
All talk and no trousers.

All smoke and no fire. (added by 89 year-old reader)

The basic idea is that il fumo (the smoke) has an odor that might take on the aroma of un arrosto (a roast) on the spit or in the oven, and might seem at first like there is something underneath it, something good to eat, but it actually has no substance. You can't eat the smoke.

Another, more literal way of saying this in Italian is: È tutta apparenza e niente sostanza (it's all appearance, but no substance).

Of course, Italians love food, and un arrosto is one of those items that is traditional fare for il pranzo della domenica (Sunday dinner). For those who like to eat meat, it smells divine as it is cooking.

Oggi [mi ha] promesso arrosto di maiale con patate.

Today she promised me pork roast with potatoes.

Caption 3, Questione di Karma - Rai Cinema

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Fumo (smoke) is used in Italian, much as we use it in English, when something goes up in smoke.

Avrebbe rovinato tutto,

He would have ruined everything,

avrebbe mandato in fumo il mio sogno.

he would have made my dream go up in smoke.

Captions 52-53, Il Commissario Manara - S1EP9 - Morte in paradiso

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Allora va tutto in fumo.

So it will all go up in smoke.

Caption 32, La Ladra - EP. 2 - Viva le spose

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Don't let your Italian studies go up in smoke!

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Let's keep in mind, as well, that fumo is also the first person singular of the verb fumare (to smoke).

Non fumo (I don't smoke).