I was fit before starting Paleo and still am. I started the Paleo diet to get rid of my acne back in 2009 and haven't gone back since.

I noticed a lot of differences when I started. I had very little energy and always felt like I couldn't do anything without eating first. I kept my same workout regimen and started losing weight. My intentions were never to lose weight, as I'm a hard gainer to begin with, so I just shortened my workouts and did less cardio. It worked and after readjusting my fat/protein/carb ratio, I was able to get back to where I was when I started.

The first two months were the worst, but it gets better once your body realizes what food actually is and what absolute filth it was receiving. My workouts now are much more intense and when I get going, there's no way you can stop me. My strength has increased and I'm able to run non-stop for 10+ miles (never could do that before).

My body still looks the same, just more defined. More importantly and the reason I am still on the paleo diet is because my face/back is clear and I'm a lot happier (since I can look in the mirror and not be in total disgust). I do get the occasional pimple, but I typically will know what caused it. I've learned so much about nutrition just by going paleo and I can't fathom returning to my old food habits. Another sweet thing I've learned is how important fats/proteins/carbs are. Just by changing the ratios I'm able to gain, lose, or maintain my weight really quickly. In about three weeks, I've lost 10 pounds. I'm happy where I'm at, so I've adjusted and now eat to maintain. It's quite amazing!

So, if you're just starting hang in there because once your body adjusts to real food, you'll feel unstoppable.

I find it helps me most with my concentration during the day. This week I started training again and it has gone well even in ketosis and fasting. Hurra! :o)

I was initially hungry a lot and a bit lethargic at times... but now my body is used to using more fatty acids for energy, so my energy levels are a lot more stable. :)

My personal experience is that I went from being a 73kg (+/- 1kg) vegetarian in 2006 with 10% BF, to 10kg heavier and still at 10% BF over a period of 3-4 years or so! I have now hit a size/weight plateau of about 84kg (+/- 1kg).

So if you were originally athletic, I'd imagine you may well get bigger and stronger, depending on how nutritionally/metabolically limiting your pre-paleo diet was.

I still look lean, but am stronger and have a bit more definition as you can see from this photo from last summer.

I wasn't exactly fit and slim, but far from any need to lose much weight. I started paleo simply b/c it made sense (after reading Taubes).

It's been over a year, and the biggest thing I've noticed is the end of chronic fatigue, the end of chronic muscle and joint pains (which are connected with my fibromyalgia). I am stronger, have bigger, leaner muscles. I can for a long time without food and feel great and energetic. My skin cleared (it's still not perfect, but much better). I haven't done blood work in a long time, but even only after a few months it improved.

My rheumatologist's medical advice on fibro was basically (after trying a few different medicines): suck it up, you can't do anything. He was pretty shocked when I told him how great I felt after switching to meat and cutting grains and sugar!

The physical change that really convinced me that something good was going on was in my hips, waist and thighs. I've always been skinny but the jiggly bits in these areas just melted away within weeks of starting Paleo. No more muffin top! My weight on the scale never changed.

Energy levels also went way up and general outlook on life is much improved.

Interesting observations, I concur largely with William I AM, it took an adjustment period of a few weeks, feeling odd during training, sweet cravings, loss of weight etc. But being fit and healthy before Paleo, I was expecting bodyfat to decrease and muscle mass to become more defined and power/strength output more effective.

After a couple of months, body adjusted, the 2-3kg weight loss was gained again (I cut back on the cardio/crossfit) and I hit PBs on most compounds, plus on TGUs, KB press, snatch cycles etc. I no longer had down periods during mid-morning, could train hard and effectively at lunchtime without breakfast if I decided on a day of IF.

Still feel hungry at times, but much less than before when insulin levels were so up and down. Usually when I forget to up the fat intake during a meal.

Overall, like most here, it takes an adjustment period, and even if you go the Paleo way despite being fit, strong and healthy with the SAD diet, you know you are doing your body/mind the world of good, and you won't look back.

I did varsity track and soccer in high school. My peak weight was 165 pushing 170 in my mid-twenties. I bloated up to 165 from just 130 in one summer. I ate 7 meals per day, iced cream, beer, (gluten-dairy based) weight gaining powder, you name it. I took creatine. I got me some man boobs but was benching and squatting heavy weight in the gym. No matter how much cardio I did, my gut remained.

In my early thirties I dropped down to about 145 because I couldn't keep eating at that pace, all that crap. I often felt too fatigued to stuff my face, generally depressed, impulsive, irritable and short tempered. Since I was in excellent physical condition, these doldrums confused me and kind of caught me off guard and made me feel like I was growing old too fast. However, I always secretly believed food greatly influences brain power and function, despite physical appearance. I found a book (Ultramind Solution) that changed my life for the best.

I went Paleo at age 34. Initially, I was shocked at the rapid weight loss but stuck with it because I felt as calm and serene as a buddhist monk. I had dreams I could levitate. People flocked to me in bars. Girls went out of there way to pry off a nice tasty morsel of the delicious contentment that oozed from my pores.

The weight loss post Paleo eventually brought me back down to 130 yet with more developed muscles than I've ever had in my life. I still look about 150 so I don't know where the weight went? Bone mass loss from lack of dairy? Internal fat that I couldn't see? I'm small but I look vicious - like a boxer in a smaller weight class.

Paleo was well worth the shrinkage. I'm in better shape at 36 than I was at 24 and I even FEEL better than I did way back then. I wish I could walk around shirtless.

How can anyone not want to get the most out of the human body and mind?

I considered myself to be in decent shape when I started. Female 5'7, 140 I ideally wanted to lose weight to get that typical slim/lean look but eventually realized I was going to have to go crazy if I wanted that body since I settled comfortably at 138 after many weeks. My stomach eventually got less bloated and toned which I can't complain about :)

Anyways, my energy went way up right away. It wasn't until I became an in-season athlete/full time student when I felt the energy drain. Which was probably due to less sleep anyways... I felt amazing while doing strict paleo, my mood was phenomenal I was on some crazy natural high for sure.

My skin and hair got better and the min I fall off the paleo wagon my skin goes nuts (worse than before). I am hyper sensitive to all sorts of things now but in some ways I'm glad because that means they were totally out of my system and my body was better functioning without toxins.

The long term affect of not eating grains/gluten has been a complete absence of allergies and colds. I never have a stuffy nose or sore throat.

I am never going back to the way I used to eat. I'm so happy I found this at 19, just wish I could help everyone realize that most health issues are a result of bad food.

I'd say the least important thing that paleo does is help you lose weight. It's almost a side effect rather than the main reason to try it.

I started off as a very active crossfitter at 6', 195-200 lbs. I always assumed that I was mostly muscle and that 200 was a good weight for me. But I was wrong! The first month of paleo sucked, I had no energy while I was transitioning to fat burner. The second month, I started performing much better than I ever did. Then all of a sudden in the third month, I dropped to 165 lbs. That's like 30-40 lbs in one month. Since then I put on a ton more muscle and I'm back up to 180 (and my clothes are smaller, so I know it's not chub this time!).

So while I technically did lose some weight (and then gain some back) on paelo, the biggest benefits to me were increased performance, no more perma-sniffle (or any kind of allergy), much better gut health, general increase in happiness. Overall just a much better life without eating the crap.

Edited to add: don't think of Paleo as a diet that you do to lose weight. Think of it as a way to cut the poison out of your system and as a result your body adjusts to what it should be. Strong, active, and not fat.

In addition to some of the great benefits above, I experienced a huge reduction in allergic responses to pollens. I used to be sneezy, drippy and puffy all throughout summer, but no more. It seems to have been both cutting out wheat entirely and reducing overall carbs that gives the best results in my case, but even just cutting out wheat made a remarkable difference.

I really wasn't healthy but might have been "fit" in a warped way (i.e. chronic cardio and underweight). I'm now at a healthy weight. Indigestion? Gone. IBS? Gone. I have Paleo to thank for many health improvements that have nothing to do with losing weight.

Early college days, Years 1 + 2:

Typical SAD. Packed down gatorade, oatmeal, cereal, grains, low fat things. But never was a processed food kind of guy (the obvious chips, junk food, was a no no.)

~165 lbs. Not fat, but looked like I could shed some.

Super cardio machine. 10 hrs of heavy breakdancing spread out 5 hrs each day Tuesday and Thursdays.

College, Year 3:

Went vegetarian/pescatarian. Reasons: Wanted to lose weight, and get healthy. Apparently I thought meat was the problem. Lost weight, and muscle mass. Dancing suffered. Activity in general suffered.

~141 lbs. I thought I was sexy. But it was kinda really unhealthy, thinking back on it. Too skinny, no strength.

Cold all the time, ate yogurt,nuts and egg white omelets like there was no tomorrow. Occasional bread. To think of it, it was pretty paleo foodwise, just severe calorie restriction, not too much attention to food quality and hidden processed stuff, and 3-4 grain exposures per month. Ate like...10 meals a day, all 100-200 calories each.

College, Year 4:

Went Paleo, after dropping vegetarianism when traveling to the UK.

~152 lbs. Pretty lean. Last bit varies with sleep, stress, and exercise. Good body composition.

Body composition is easy to keep. Stronger, but still in beginning strength stages. Can't seem to get excited about much... Exercise sometimes tanks it. Lack explosive power in my movements...Still trying to hash that out, with much difficulty. Diet is pretty good all the time. No cravings, no desires to cheat. Just feeding well, 2 large meals per day, attention to food quality is a must.

Present:

Best body composition seems to occur with: high fat, mod protein, low carb, 2 meals a day, sorta IF schedule.

Seem to have lost my explosiveness, both in breakdance, and normal activity. Really kind of stoic...and when I dance, it's very calm and controlled. This is the only thing that worries me.