If you are short and fat then to look tall and slim you will wear:

Concept:

Selection of clothes:

• Clothing should be chosen based on the season, age, occasion, income, style, and body type.
• Through clothing, one can draw attention to specific personality traits and, to some extent, conceal imperfections in their physical attributes.

Explanation:

Full-length dress whose cut is the princess line:

• The princess line refers to the absence of a horizontal join or division at the waist in a woman's fitted dress or other item fashioned in long panels.
• Instead of employing darts to shape the garment, long seams (also known as princess seams) and contoured pattern pieces are used to get the desired fit.
• When they fit properly, princess line dresses with full length are attractive because they help to produce lean, elegant lines.
• The curvier woman can wear them best.
• The vertical seam lines lengthen the torso, define the waist, and direct the eye upward.

Thus, if you are short and fat then to look tall and slim you will wear a full-length dress whose cut is the princess line. 

Additional InformationVertical Lines:

• By highlighting length and downplaying width, vertical stripes and patterns deceive the eyes into perceiving a taller body.
• As a result, they are slimming as well as elongating.

Horizontal Lines:

• Horizontal lines should be worn with caution.
• If you would not want to appear bigger and shorter, for instance, avoid wearing them at your neckline and midsection.

Diagonal Lines:

• By drawing attention away from the body's true mass and width, diagonal lines help people look slimmer.