N=1 but I lost over 100 pounds in 8 months by changing to a keto diet with zero exercise (consciously going even more sedentary than I already was) and have kept it off for over eight years now. After I reached my ideal weight I restored exercise to my previous normal level (which is minimal but not absolutely sedentary). After a year I slowly transitioned from strict keto to low carb for life.
I feel great, look good and my health improved dramatically. Before changing I was on meds for pre-diabetes, high blood pressure and poor HDL/Trig along with having bad apnea and tectonic snoring. All resolved after 8 months and still off the meds today. In the prior decade I'd spent a lot of effort and money trying various diets, including medically supervised, but they were hard, stressful and none worked long term. Even though I've never been athletic or remotely a gym-rat, intentionally going sedentary was an unusual choice because I'd always heard "eat less, move more" but exercise made me hungrier. So when I got serious about doing keto hardcore, I decided to pause even the minimal token "faux exercise" like an occasional pleasure bike-ride or short walk on weekends.
Frankly, that occasional, brief exercise probably never did anything in terms of weight loss anyway but it did provide a psychological excuse to slip on diet. So eliminating that excuse and putting all my focus on diet may have been the main benefit of going zero exercise during my weight loss period. After I got below my target 'dream weight', I returned to my usual minimal exercise and since then it's increased even more because now I actually enjoy exercise. It turns out that exercise is a lot more fun when you're not obese and winded after 90 seconds! I think Keto worked for me when other diets hadn't because it's so strict but also brutally simple. I've also always liked the low carb foods like meats and cheeses.
As a significant and long-term success case, I'll share my personal "keys to keto success": 1. Commit to doing it hardcore for at least 30 days. 2. Rigorously track every molecule of food intake in a tracking app for the first month. Yep, get measuring spoons and a kitchen scale for weighing things. Think of it as a cool lab experiment and you're the rat. Get used to cooking at home and bringing lunch to work until you get the hang of the low carb lifestyle. 3. For the first week do not track calories, just limit carbs religiously. Seriously, stuff all the calories you want. Steaks drenched in butter and sour cream, a quarter pound of cheddar, whatever. Why? The first week is the hardest and this makes the transition easier. The calories will be much easier after you get control of your blood sugar by limiting carbs. 4. You MUST supplement electrolytes (sodium & potassium) for at least the first week. "Keto Flu" is real, excruciating and so easy to avoid. I didn't take all the warnings seriously and failed my first attempt at keto in utter misery after just 38 hours. 5. Start on a quiet weekend where you can just focus on this from Fri afternoon to Mon morning. 6. Absolutely, positively DO NOT CHEAT on carbs for the first 30 days. Keto is different because the first 3-ish days of transitioning off carbs are pretty hard. If you cheat, you'll keep having to redo some or all of that transition over and over. It's like crossing a wall of fire. You can get through it fine the first time with focus and planning but you definitely do not want to be wobbling back and forth through it. Keto works because strictly limiting carbs controls blood sugar which reduces hunger making cutting calories much easier. If you need to cheat, cheat on calories not on carbs.
It's not as hard as it sounds. Just get past the first month and it all gets a lot easier. The results come fast. I lost 10 pounds in 10 days and 20 pounds in 30, which provides a lot of motivation! At around six weeks I became 'fat-adapted' which is a long-term metabolic transition to primarily burning fat instead of carbs (glucose) for energy. It felt absolutely amazing in every way - physically, mentally and emotionally, like nothing I'd ever experienced before. I was mentally sharper, physically quicker and emotionally more grounded in a positive mode. Everything just felt and worked better in subtle but tangible, meaningfully real ways. It made me never want to go back to living inside a primarily carb-adapted metabolism. Of course, I hadn't physically craved carbs since the first month and by around 60 days my old habitual eating patterns and reflexes had faded. Then at around 90 days my palate shifted, meaning I even lost my taste for carbie foods. If I tried a small bite of something carb-laden that I'd loved my whole life, it didn't even taste particularly good to me anymore. I also became hyper-sensitive to sugar. Sugar-soaked foods just taste poisonously over-sweetened (which they kind of are). A normal apple now tastes as sweet as I'd ever want, like a dessert that has extra sugar-added.
For most of my life my weight was a metabolic mystery seemingly out of my control. Today, it's hard to even remember what it was like being a slave to my raging blood sugar and constant hunger. Now I feel closely attuned to my body. This makes my weight and appearance an almost trivial conscious choice. Fortunately, going low-carb is a lot easier today than when I started in 2017. There are many more delicious low-carb food choices at the grocery and everyone has heard of keto so it's not as weird. Even Wal-Mart has a selection of keto-breads and, recently, bagels! Standard disclaimer: Every metabolism is different and what worked so effectively for me may not work as well for you.