With all the focus on celebrity weight-loss, one star is walking a different path. As many boast how many pounds they've shed, Rihanna is bragging up weight gain, and Twitter is singing the praises of the new "Thickanna." Riri and fans were worried about her "anorexic" weight-loss. Recently, the "Umbrella" singer looks curvier in the buttocks, thighs and breasts. With a tummy still just as flat, folks have wondered if she had plastic surgery such as a boob job or butt lift.

Rihanna rejoices at weight gain

Well, there's a turn up for the books -- someone who wants to get fatter! Actually, other celebrities like Sarah Hyland of "Modern Family" dislike being thin and would love to put on some pounds.

Hyland made it clear that her weight-loss was not due to an eating disorder. She's been on bed rest following an undisclosed illness, possibly related to her kidney replacement. Riri has no idea why she keeps losing but says her hectic schedule creates anorexia-like eating habits. She bemoaned having no "boobs or butt" and was indeed very petite until recently.

RiRi shows odd weight patterns

Lately, the singer -- born Robyn Rihanna Fenty -- has been showing much heavier legs, buttocks and breasts, which have earned her the nickname "Thickanna." Her legs and thighs have always been "thicker" but overall, RiRi appears underweight. Now, she looks almost overweight, but only in certain areas. Typically when people gain, they do it all over. In fact, the stomach is one of the first areas to increase.

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And belly fat is the last to go in weight-loss. But Rihanna's tummy looks as small as ever.

Plastic surgery highlights weight-loss

When celebrities show unusual weight gain or loss in just one area, plastic surgery is the logical explanation. Mariah Carey boasted weight-loss last year but physician's suspected some kind of tummy tuck. And Kim Kardashian is known for her legendary backside, enhanced by thigh and butt implants. Mama June got breast implants to highlight her smaller stomach after bariatric surgery and a tummy tuck.

The "My 600-lb Life" resident doctor (Dr. Now) does skin removal surgery on obese patients to get rid of loose skin after gastric bypass surgery. Rihanna doesn't show any signs of scarring left from plastic surgery, but that doesn't explain how some parts got miraculously larger.

How Rihanna got bigger butt and boobs

The 29-year-old Grammy winner says she has no idea why she got smaller nor why she is getting bigger. Plastic surgery is a possibility that she may feel uncomfortable admitting. Compare the images in the video above. Since 2012, Rihanna's chest appears some 2-3 bra sizes larger while the rest of her looks the same. This suggest a breast implant procedure. Her thighs and buttocks have increased too. Was a Brazilian butt lift involved? Or has Riri just been taking better care of herself and cleaning up her eating habits?