The 1930s Tango Diet
The dieter meets with a tango aficionado once a week (or so) and tries to translate, without a dictionary, two or three tango songs of the aficionado's nation.
Pluses: Deeply engaging lyrics, improves cultural knowledge, develops excellent party tricks.
Minuses: Arguments over whether all women are like the trollops in tango songs or not. Vocabulary limited to words needed for doomed love affairs. Growing sense that absolutely everything was better before September 1939. Accidental membership in partia KORWiN.
The Fluent Forever Diet
This popular diet is based on the self-help guide Fluent Forever by Gabriel Wyner. It involves making a Leitner box--a collection of carefully spaced vocabulary cards, either electronically or literally.
Pluses: The "no English, no translating, images straight into the brain" philosophy makes sense.
Minuses: It takes hours of time and the discipline of a Desert Father to make and memorize even a few hundred cards, and you can't take a physical Leitner box with you on the bus. Trying to come up with images to illustrate grammatical concepts, let alone sentence structure, is extremely difficult, and just the thought of making a separate card for each case of each noun in (say) a Slavic language is enough to make you cry like a [click: xxx].
The Harry Potter Diet
This ingenious diet involves reading the entire Harry Potter series in the target language, and listening to the audiobooks read by a native speaker.
Pluses: Harry Potter materials are easily found in a plethora of languages and the rapid-paced plots should keep you going.
Minuses: Unless you stop and memorize every word you don't understand in The Philosopher's Stone, you will begin to go crazy. But then the pace will be so slow, you risk going crazy anyway. Also, Harry is clearly so stupid about Tom Riddle, you may lose all patience halfway through The Chamber of Secrets.
The Sienkiewicz Diet
This diet forbids reading target-language translations of English stuff. Tailored for Polish as a Foreign Language learners, the Sienkiewicz Diet involves reading Polish children's classic In Desert and Wilderness in the Polish original and listening to an audiobook featuring a Polish actor.
Pluses: Virtuous feeling of authenticity. Ability to tell native Polish readers you are reading Sienkiewicz.
Minuses: Vocabulary so complicated and archaic that even native Poles need to look it up in a dictionary, and when they tell you this, your already shaky resolve collapses.
The Polish in Four Weeks Diet
Tailored, naturally, to PFL learners, this highly effective diet employs the textbooks and CDs of Polish in Four Weeks to build Polish vocabulary and listening skills.
Pluses: Each chapter has an engaging plot, featuring the drama and shouting typical to Polish life. Can be tweaked for maximum efficiency (see Brain Blitz Diet below). There is a second volume, also called Polish in Four Weeks.
Minus: Takes much longer than four weeks to complete.
The Brain Blitz Diet
Not for the faint-hearted, the Brain Blitz Diet involves memorizing, not just sentences, but entire blocks of target-language text, repeating them aloud as you write them out again and again and again.
Pluses: It works. The only method that works better than the Brain Blitz diet is full immersion in a country where the target language is spoken + vodka.
Minuses: Involuntary loss of control over speech, leading to a tendency to exclaim, apropos of nothing "Jak to? Does Sir not know? We're playing France! It is today? Completely I forgot. Good that Sir reminded me. What you think? Have we chances?" Development of errors, in English punctuation. Strain on marriage if monolingual spouse objects to being addressed in target language.
CONCLUSION: All these fad language diets can contribute to fluency in a target language although the only one by which one can absorb the complex sentence structures of non-Romance languages is, unfortunately, the Brain Blitz Diet. It hurts, but it works.