"Is it Working?"
The truth is all of these "diets" could work. The opposite is also true, all of them could be totally wrong for you as an individual. If you ever hear someone say that this way of eating or that way of eating is the best way, my advice is run the other way!
Humans and the environments that they live in vary so much that there is no one size fits all diet. There are some common themes that science is showing gives people the best chance to be healthy and lose weight. Eat more vegetables and eat fewer processed grains and sugars. After that everything else is pretty much up in the air.
This is where that question, "Is it working?", comes into play. In order to get results I think you need to ask this of your current diet and fitness regime at a minimum of every 3 months and a maximum of every 1 month.
Why that time frame?
It is possible to over manage your choices...that's why I like 1 month minimum. You need to give things a chance to take hold and your body needs to adapt to the changes you are making. The concept of 1 step backwards to take 2 steps forward totally applies. Our bodies may have some perceived negative results before the good stuff starts happening. For example, if you start weight training, you are going to be causing inflammation in your muscle tissue which leads to extra retained water and therefore added weight and size. Also going from S.A.D. to a more plant based diet may cause some digestive distress initially due to the added fiber, but that will regulate after a couple weeks most likely. Point being, give it some time!
On the other side, if you aren't asking the question at least every 3 months then you might be wasting effort and resources. Which will eventually cause a person to go crazy and throw in the towel. If your goal is to lose fat or change your body composition, this makes it super important to track your weight, measurements and take photos. Without proper tracking you won't know if what you are doing is working. Three months should be enough time to make progress on a given plan unless a person has major medical issues. If you haven't seen progress I would recommend making fairly minor changes to begin. Some things that could mean would be; eating more or less food, recalibrating the %'s of calories you get from different macronutrients, or increasing your compliance (fewer treats), or switching up the intensity/duration of your workouts. Or as simple as adding a multivitamin or fish oil supplement. You don't need to go from a straight Paleo diet to Vegan if you haven't seen the scale budge after 3 months. Start small, but make adjustments.
If you have a decent knowledge of fitness and nutrition you can probably make these small tweaks yourself. You can use an app like My Fitness Pal to track calories and macronutrient %'s. If you aren't keeping a food journal, START!!! That will help you understand if you are actually eating the foods that you think you are. In the journal you can also track how foods are making you feel and maybe identify foods that cause distress in your body and eliminate those.
If you are novice or beginner, i.e. you had to google macronutrient, then I would recommend reaching out to someone that is trained. Chances are you want results sooner rather than later. Working with somone that is trained will help you get you going in the right direction faster and be able to make more educated tweaks to your plan. Your time is valuable and your health is important, make the investment!
I'll close with this, when you are analyzing your progress, don't just focus on weight or measurements. Your exercise and diet should maximize your health and performance too. Make sure you factor in those things when figuring out if you are making progress. It's really easy to lose weight if you just stop eating...but you will lose weight really fast and your health will deteriorate. If you lead with HEALTH, the performance and body composition will usually fall into place.