FATTENING. I hate this word. It is often used to express fear about the perceived power that a food is thought to have on one’s weight and shape.
“This is SO fattening….gross!” 
At it’s root, lies fatphobia – the fear of fat or getting fat, or being fat. For one, the concept of that a food could “add fat or weight” instills fear that something is wrong with adding weight. This thinking stigmatizes fat bodies. Saying these things, expressing dread, horror and fear, is insulting to your fat friends, and family members. Plus, it’s scientifically inaccurate. One food does not have the power to cause weight gain.
Diets need fat. Foods with fat make food taste good, and helps to keep us full. We need fats for hormone production like estrogen, or If you’re looking for a testosterone booster, absorption of vitamins A, D, E, K. And foods with fat are often very yummy.
These foods include oils, avocado, nuts, nut butters, trail mix, cookies, brownies, ice cream, etc.
Those with eating disorders may be scared to include these foods as they may have cut out these in the throws of their eating disorder. Adding these foods, through exposure, will help clients be more free.
Those with eating disorders may also be scared to gain weight, yet it is often necessary for them to reach medical, nutritional and psychological goals. This includes metabolic recovery, restoration of vital signs, normalization of hormones (estrogen/testosterone), improvement of bone density, return of energy, improvement of mood/depression/anxiety, improved sports performance (endurance, muscle gain, recovery, reaction time, coordination), improved concentration, and many others.
There are some words and phrases that it’s time to leave behind.
“Fattening” is one of them.
Also, Stop Saying “I Feel Fat” if You Aren’t
Marie Southard Ospina writes it perfectly in the 1.6.20 blog on the Temper:
“When you are not fat yourself, but you use a phrase like “I feel fat” to belittle your appearance, what you are saying to those around you — in particular those who are actually fat — is that you feel like you look like them and that their type of body is a ghastly, ugly, wretched thing.
Often times when I hear this, it’s obvious that what the person is really trying to say is that a certain outfit makes them feel frumpy, or maybe that they haven’t slept well and are looking a little more haggard, or that they haven’t eaten a vegetable in some time and feel a little meh as a result. So, rather than insulting someone else’s body, and a whole lot of other people in the process, consider saying what you actually mean.”