You train hard with both weights and cardio, but for some reason you're still not lean. Sound familiar? If so, you may find yourself wondering how it's possible to seemingly do everything right and still not see a ripped physique in the mirror.
If you're honest with yourself and reflect a little more, however, you may admit to one or more of these factors holding you back: too much fast food, sporadic training habits, underwhelming workouts, or even a wicked sweet tooth.
But those are pretty obvious. What about hidden saboteurs? Let's identify the most common culprits derailing your efforts to dial it in. Below are five reasons you aren't ripped that can easily hamper your efforts to burn body fat and blur your abdominal definition. Address each one and you might finally make being ripped a reality!
1

CUTTING YOUR CALS TOO QUICKLY

A common problem many dieters make is dropping calories and carbs too drastically right out of the gate. I get a lot of questions from people asking about going on a ketogenic (keto) diet—which is an extremely low-carb diet—to get ripped. Honestly, dropping all your carbs in one fell swoop is the last thing you want to do!
Yes, a drastic cut in your carbs can lead to a big drop in bodyweight, but that drop will be short-lived. The problem with dieting is that your body is constantly fighting to prevent too much fat loss; after all, fat is a great energy reserve if times get tough and food is no longer plentiful. While that may have been a problem for our ancestors, it's not a real issue for most of us today.
So no matter how low you drop carbs (and calories), your body will eventually adjust to your new caloric intake. If you've dropped most or all of your carbs, your body will adjust to that low-carb intake and you won't have room to cut further. Where do you go from there when you're no longer losing body fat?
The real key to dieting is to eat as much as you can while still losing body fat. Then, when you reach a plateau, you make a small cut in carbs and calories so that when you plateau again, as you inevitably will, you can make another drop and can continue losing body fat.

"THE REAL KEY TO DIETING IS TO EAT AS MUCH AS YOU CAN WHILE STILL LOSING BODY FAT. THEN, WHEN YOU REACH A PLATEAU, YOU MAKE A SMALL CUT IN CARBS AND CALORIES."
I usually start clients off on a diet by having them record at least three days of eating on their current meal plan, which I use to calculate their average daily calorie intake. I use this number as the starting calorie intake for the diet. 
I then alter the macronutrients so that within those calories they're consuming 1.0-1.5 grams of protein per pound of body weight daily and about 0.5 grams of dietary fat per pound. The remaining calories come from carbs.
Here, I usually round carbs down a bit so that there's a small reduction—about 200 fewer calories per day—from what their eating plan initially listed. This sets my clients up in a slight caloric deficit, which will help them begin losing fat.
I suggest you follow a similar process until your fat loss plateaus, at which point you'll reduce your carbs by about 0.25 grams per pound of body weight. Each time a new fat-loss plateau is reached, reduce carbs by another 0.25 grams per pound.
For example, in the initial fat-loss phase, if a 200-pound person was eating 1,200 calories from carbs (or 300 grams), which is 1.5 grams per pound of body weight, a 0.25 gram drop in carbs would put him at roughly 250 grams of carbs, which equates to a reduction of 50 grams of carbs and 400 calories from his daily diet.
If it were you in this example, you'd counter each subsequent fat-loss plateau with another drop of roughly 50 grams of carbs.
2

NOT HIIT-ING IT

One misconception that's been perpetuated in bodybuilding circles for decades is that you must do low-intensity cardio to maximize fat burning and spare muscle mass. Yet the research and what we're seeing in the gym today points in the exact opposite direction.
Studies having shown that those who do some form of high-intensity interval training (HIIT), which alternatives cycles of all-out training with slower recovery phases, lose about twice as much body fat as those who do steady-state (slow and steady) cardio. And this is despite the fact that those doing HIIT spend far less time exercising!1-7
In a nutshell, HIIT results in less time spent doing cardio, and way more fat being burned. 
This is because HIIT increases your post-exercise metabolism, which boosts the calories and fat burned while you're not exercising.
As far as sparing muscle goes, both lab research and real-world experience show that those performing HIIT either lose no muscle or actually gain it. As an easy example, consider the muscle mass of a sprinter compared to a long-distance runner. The high-intensity training the sprinter does helps build muscle, not sacrifice it. The long-distance runner who trains at a slow, steady pace has far less muscle mass.
HIIT can take several forms. A typical HIIT session consists of all-out effort, such as sprinting, alternated with low-intensity intervals of active recovery, like walking. For specific examples of HIIT workouts as well as a more detailed explanation of the science behind HIIT.
One particularly great form of HIIT is Tabata training, which has become hugely popular in recent years among CrossFitters and other serious gym rats. One bout of Tabata involves eight 20-second all-out work intervals alternated with 10 seconds of rest, totaling just four minutes.

KETTLEBELL SWINGS

For example, you could do 20 seconds of kettlebell swings followed by 10 seconds of rest for eight cycles, or you could sprint for 20 seconds and walk for 10 seconds, again eight times through. In only four minutes, you'll get an absolutely killer workout!
Few people realize that my popular cardio-acceleration technique is also a form of HIIT. With cardio-acceleration, you do around 60 seconds of high-intensity exercise—such as running in place, kettlebell swings, bench step-ups, or sprinting—between sets of your weight-training workout.
For example, if you were doing three sets of bench presses, after reaching muscle failure on the first set, you'd go right into 60 seconds of, say, bench step-ups. Then, when you're done with the step-ups, you'd go right into your second set on the bench press. Your entire workout would be done in this manner.
3

LIFTING TOO LIGHT

Another misconception about training for fat loss is that you should opt for light weight and high reps to get lean. This misconception is probably the result of thinking that higher reps means more work performed, which can help you burn more calories. But it's not just about how much work you do, but also how the work you do affects your body and your metabolism.
Similar to HIIT cardio, research confirms that using heavier loads in your workouts results in a higher metabolic rate post-workout as compared to light weight. What does this mean? More calories burned!

BENCH PRESS

At the Norwegian University of Sport and Physical Education (Oslo), researchers analyzed multiple studies and concluded that training with heavier weights for fewer reps may elicit a greater and more sustained rise in resting metabolic rate (following the workout) than training with lighter weights and higher reps.8
By "heavier weights for fewer reps," I'm talking about a load that limits you to 8 reps per set, and training to failure. This will boost your metabolic rate more and keep it that way for longer after the workout ends than those 20-rep sets everyone thinks are getting them shredded.
4

TAKING TOO MUCH REST

Another area that may be hampering your fat-loss efforts is all the time you waste in the gym between sets. If getting shredded is your goal, you should spend as much time as possible moving in the gym, not standing around.
Bottom line: Minimize your rest time between sets. Researchers from the College of New Jersey discovered that when subjects rested 30 seconds between sets on the bench press for 5 sets of 5 reps, they burned a little more than 50 percent more calories than when they rested three minutes between sets.9
I suggest turning your rest time into work time via supersets or cardio acceleration. As discussed earlier, cardio acceleration can save you time in the gym and further enhance fat loss. Supersets involve doing two exercises back to back, either for two different muscle groups (such as a chest exercise followed by a back move), or for the same body part (such as two quad exercises).

"I SUGGEST TURNING YOUR REST TIME INTO WORK TIME VIA SUPERSETS OR CARDIO ACCELERATION."
Research shows that using supersets can increase calorie burn both during a workout and afterward by around 35 percent compared to standard straight sets.10 So don't sit down after you finish your set!
5

SITTING FOR TOO LONG

What you do when you're not in the gym may further be compromising your fat-loss efforts, not to mention your health. Research from Australia found that, out of more than 2,000 subjects who exercised vigorously for a minimum of 2.5 hours per week, those who watched more than 40 minutes of television per day had higher waist circumference, blood pressure, and blood-glucose levels than those watching fewer than 40 minutes.11

The researchers theorized this may be due to the fact that, when you sit for prolonged periods, your body's ability to burn fat is severely compromised. This was supported by researchers at the University of Missouri (Columbia) who reviewed studies done in both animals and humans and found that prolonged sitting severely blunted the activity of enzymes involved in fat burning, particularly lipoprotein lipase.12
Other research also supports a link between the amount of time spent sitting during the day and body-fat levels, as well as negative health implications. A 2012 meta-analysis of 18 studies by University of Leicester (England) researchers found that those sitting for extended periods throughout the day, even if they exercised regularly, had a significantly greater risk of diabetes, heart disease, and death.13
A more recent meta-analysis by scientists at the Toronto Rehab, University Health Network (UHN), and Institute for Clinical Evaluative Sciences analyzed 47 studies on sedentary behavior and reported that regardless of exercises habits, sitting for long periods increases the risk of disease and early death.14

"AVOID A FAT-BURNING SLUMP BY STAYING ACTIVE THROUGHOUT THE DAY."
The take-home here is simple: Avoid a fat-burning slump by staying active throughout the day. If you sit for long periods at work, try getting up and stretching or walking to the fridge or water cooler at least every 20 minutes or so. 
Do the same if you're sitting at home in front of the TV or computer. When you're shopping or running errands, park far away from store entrances to increase total walking distance. 
Even better, walk or bike to run your errands when possible instead of driving. Avoid elevators and escalators and take the stairs whenever you can.
Seizing all of these opportunities for physical activity can add up to a lot of extra activity, which can keep your fat-burning engines primed and your health optimized. At that point, you won't need to look for reasons you're not ripped—because you'll be ripped!
REFERENCES
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  2. Tremblay, A., Simoneau, J. A., & Bouchard, C. (1994). Impact of exercise intensity on body fatness and skeletal muscle metabolism. Metabolism, 43(7), 814-818.
  3. King, J. W. (2001). A comparison of the effects of interval training vs. continuous training on weight loss and body composition in obese pre-menopausal women (Doctoral dissertation, East Tennessee State University).
  4. Meuret, J. R., Sirithienthad, P., Moffatt, R. J., & Panton, L. B. (2007). A Comparison Of The Effects Of Continuous Aerobic, Intermittent Aerobic, And Resistance Exercise On Resting Metabolic Rate At 12 And 21 Hours Post?Exercise: 2153: Board# 66 June 1 8: 00 AM?9: 30 AM. Medicine & Science in Sports & Exercise, 39(5), S384-S385.
  5. Sijie, T., Hainai, Y., Fengying, Y., & Jianxiong, W. (2012). High intensity interval exercise training in overweight young women. The Journal of Sports Medicine and Physical Fitness, 52(3), 255-262.
  6. Treuth, M. S., Hunter, G. R., & Williams, M. A. R. T. H. A. (1996). Effects of exercise intensity on 24-h energy expenditure and substrate oxidation. Medicine and Science in Sports and Exercise, 28(9), 1138-1143.
  7. Boutcher, S. H. (2010). High-intensity intermittent exercise and fat loss. Journal of Obesity, 2011.
  8. Børsheim, E., & Bahr, R. (2003). Effect of exercise intensity, duration and mode on post-exercise oxygen consumption.Sports Medicine, 33(14), 1037-1060.
  9. Ratamess, N. A., Falvo, M. J., Mangine, G. T., Hoffman, J. R., Faigenbaum, A. D., & Kang, J. (2007). The effect of rest interval length on metabolic responses to the bench press exercise. European Journal of Applied Physiology, 100(1), 1-17.
  10. Kelleher, A. R., Hackney, K. J., Fairchild, T. J., Keslacy, S., & Ploutz-Snyder, L. L. (2010). The metabolic costs of reciprocal supersets vs. traditional resistance exercise in young recreationally active adults. The Journal of Strength & Conditioning Research, 24(4), 1043-1051.
  11. Healy, G. N., Dunstan, D. W., Salmon, J. O., Shaw, J. E., Zimmet, P. Z., & Owen, N. (2008). Television time and continuous metabolic risk in physically active adults. Medicine and Science in Sports and Exercise, 40(4), 639.
  12. Hamilton, M. T., Hamilton, D. G., & Zderic, T. W. (2007). Role of low energy expenditure and sitting in obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease. Diabetes, 56(11), 2655-2667.
  13. Wilmot, E. G., Edwardson, C. L., Achana, F. A., Davies, M. J., Gorely, T., Gray, L. J., ... & Biddle, S. J. (2012). Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis.Diabetologia, 55, 2895-2905.
  14. Biswas, A., Oh, P. I., Faulkner, G. E., Bajaj, R. R., Silver, M. A., Mitchell, M. S., & Alter, D. A. (2015). Sedentary Time and Its Association With Risk for Disease Incidence, Mortality, and Hospitalization in Adults: A Systematic Review and Meta-analysis. Annals of Internal Medicine, 162(2), 123-132.