1. You're Doing a Diet
If you have a diet mentality, you'll get a diet result. Diets by their very nature are short-term. The vast majority are based around removing a food group or groups, and with this withholding from ourselves comes boredom, resentment, and cravings - which usually result in a 'going crazy' period at the end of the diets time-frame. Congrats! That 5kg in 3 weeks you just lost will be back with interest.
Any short-term approach will have short-term results. See point 2.
2. Any Diet Will Work....... short term
Everyone has a story about the diet they (or a friend) did that lost them a bunch of weight. No kidding, that's what happens when you restrict the body of its nutritional needs. It starves. There shouldn't be any enthusiasm for this kind of result - just awareness that a train wreck is sure to follow. If you want to save some money for the future do you save a sum of money once only, or save a small amount regularly over time? If you want to enrich your marriage do you do one nice thing for your partner ever, or lots of little things regularly?
There's no way around the fact that some effort sustained for a long (life) time will out do a short blast. That counts for everything in life!
3. Your Body Likes Same-ness
Your body likes where its at now. It doesn't want to change. It's been like that for 15 years and getting it to change in 3 months is not a realistic expectation. The human body is designed for survival. Storing body fat is what it does. It helps raise our chance of survival, and that's why we're so good at doing it. When you introduce a diet to your body it will resist your attempts as best it can as it sees this change as harmful to its homeostasis.
To make a long term change you're going to have to invest some time, and make change slowly and consistently.
4. You Aren't Just a Number on the Scales
Human physiology is a complex beast. There's a reason that diets have been around for a hundred years, yet we are overall fatter, sicker, and less active than ever. Our bodies don't react to the catchy name of a diet or convenient quick to prepare meals - they react to the nutrition we choose to put in them. Anything and everything we ingest (among other factors) affect our energy, moods, hormone levels, ability to regulate stress, recognition of hunger and feeling full, and many other small daily systems that constantly affect our body and keep it running. Mess with these and you not only see the number constantly up and down on a scale, but you'll do deeper harm to your long term physiology and your bodies ability to reach its optimal health levels.
5. Your Heads All Wrong
If there was a magic diet, don't you think everybody would be doing it now? The clever company who'd developed that diet would be rich, everyone would be on it, and we'd all be in amazing shape. Unfortunately that's not the case, and never will be the case! It will always come down to the individual responsibility of what we put in our mouths. For any company recommending a diet, the ultimate result for them is to make money.
As long as this is the case there will always be a new diet to resist. The best way to resist this is to know that you are eating healthily for life. Using (very un-sexy) sensible eating guidelines that don't come with a cool #@leo type name, a special cookbook, or a magic blender. This type of eating requires patience, educating yourself, the ability to cook (at least simply) and the confidence to stick to this path as you're bombarded on all sides by new diets.
That's why at Results Room we don't use a diet. We recommend our Real Food Programme. It's nothing more complex than increasing the amount of real food in your life, while reducing the amount of fake food. Nothing is off limits, but there's education around why or when we eat fake foods, and how they balance out with our activity levels and lifestyle.
Sexy diet? No. Sexy results longterm? Yes - if you avoid a diet mentality and follow the programme long-term.