I need some tips for losing weight for my friend who is on the Porkier Side.
Is there also a Catholic Saint that encourages a healthy lifestyle?

Why is he on the porkier side?
Does he eat like a pig?
Does he get enough exercise?

As for saints, you could take your pick, but not one who lived on the Blessed Sacrament alone.

Seriously, Blessed Margaret of Cortona, St Charles Borromeo.
St Thomas Aquinas was supposedly on the porkier side. 

Less sugar.  No likes to hear, less glutens.  Sugar holds water. Water is weight.  Find things you can have, like dates with coconut or almond nuts, at sprouts.  Almond milk/coconut no sugar. No aspartame, or surcolose. No sodas, but spritzers. Substitute pasta for spaghetti squash. Never cut the squash, have produce dept. do that. Did you ever try an acorn? They are so good. produce dept to cut in half. bake at 350 for about half an hour and put butter, little honey and cinnamon. Yum tastes like pumpkin pie.

I like making fruit smoothies, using the almond milk, any fruit, almond yogurt.  cookies, go to the book, Breaking the vicious cycle.  It is written for those with irritable bowel syndrome.  Has knowledge  and recipes. Monster cookies made with almond flour.

When I make my smoothies and freeze in icing containers and take out a thaw when I wish.  That is how I try to keep 15 lbs off, so as not to have blood pressure meds.  If you have high tryglicerides use liquid fish oil. a tablespoon 1 hour before or 1 hour after you eat, OR it won't work.

Is this what you had in mind?  BTW, where is this ski resort?  

I was always to the Assumption that the Aquinas being fat was a Luther Lie to create the idea that he lived in luxury as a Monk

Nup. He really was fat. He was ridiculed as 'the dumb ox'

St. Thomas Aquinas (1225-1274) is the most famous of the fat saints. Known as the dumb ox for his customary ponderous silence and his girth, Thomas ran from the prestigious Benedictine vocation arranged by his family to become one of the Dominican Order’s greatest thinkers of all time. Contemporary accounts call him “large and heavy” and “very fat,” though the story that he had a hole cut out of the table to fit his belly may be purely legendary. What a mercy for the entire Church that Thomas was unconcerned with anyone’s opinions, and spent his time in prayer and study rather than spending his life pursuing thinness.

https://aleteia.org/2021/01/02/saints-who-help-us-love-our-bodies/

Just do intermittent fasting.  Eat all your calories in a 4 to 6 hour window.  Try not to eat 3 hours before bed.  Don't limit yourself on what you can eat necessarily.  In my opinion that's what kills those diets.

Agree with this advice.

Additionally keeping track of calories is helpful; you can always change to healthier food as you go along, but persistence is key.

Just do intermittent fasting.  Eat all your calories in a 4 to 6 hour window.  Try not to eat 3 hours before bed.  Don't limit yourself on what you can eat necessarily.  In my opinion that's what kills those diets.

THIS ^^^ ...

Intermittent fasting, where you eat all your food within about an 8-hour window.  During the window, maintain a reasonable number of calories based on lean body mass.  If you fast intermittent but squeeze 4,000 calories into the window, it won't help you too much.  Perhaps a tiny calorie deficit will help the process along, but do not make it too big a deficit or the metabolism slows down, and people who are miserable tend to crash off of diets.  I would also limit carbs a little bit.

If I know that I can eat from 10:00 AM to 6:00 PM (slightly smaller window is better, say, 11:00 AM - 5:00 PM), and am limited to a reasonable number of calories, I'm not going to waste the calories on a sugary soft drink.

Make sure to get good amounts of protein and healthy fats, at the expense of carbs, but you don't have to go total "Atkins" to lose weight on Intermittent.

There are lots of scientific studies now about the amazing benefits of fasting, where the body has a chance to heal, reset itself, and detoxify.

I agree that diets that make people miserable, severe calorie deficit, or total Atkins, people tend to just crash off those things and then go into binging where they get bigger than even before.

Of course fasting will have the opposite effect for those with adrenal fatigue and post-menopausal women will have very little success with keto alone.  Calorie restriction will still be required (burn more than you consume).