So what forms the basis - what are the necessary conditions for us to lose fat?  To lose fat you must create a calorie deficit.  Simply put, a calorie deficit refers to consuming less energy (i.e. food) than your body requires or expends in a given period of time (typically measured within a 24 hour period).  Now, the common MISTAKE made by dieters and CICO “deniers” is assuming that CALORIES IN literally refers only to the total (known) numerical value of calories eaten/drank and that CALORIES OUT literally refers only to calories “burned” through exercise - and for some slightly more acquainted with bioenergetics, resting metabolic rate.

CALORIES IN
Calories-In is relatively simple: it’s the food you digest.  However, the calorie content of food is imperfectly determined and calorie availability can vary between species/variety/source and even due to the degree of processing involved.  These are small inconsistencies, but inconsistencies nonetheless.  For example, dietary fiber cannot be digested through typical enzymatic action in our small intestine (we do not produce cellulase).  So even though fiber HAS calories, it doesn't mean we "absorb" those calories.  However, gut flora in our large intestine can - through fermentation - convert fiber into short-chain fatty acids.  Those SCFA can translocate from the intestinal lumen into circulation, yielding calories.  Thus, the composition of your gut flora influences your CALORIES IN, and that composition differs between people, and across your lifespan.

CALORIES OUT 
This gets more complicated.  CALORIES OUT is not simply represented by what the treadmill tells you.  You inhabit a living body that, whether you are conscious of the fact or not, is perpetually dependent on energy availability.  In short, CALORIES OUT may be summed up as:

• Basal Metabolic Rate (BMR)
• Non-Exercise Activity Thermogenesis (NEAT)
• Exercise Activity (EA)
• Thermic Effect of Food (TEF)

Most people only consider EA when calculating their calorie expenditure, but this is only a fraction of it.  BMR refers to the energy required to “keep the lights on” - the energy needed to keep your organs functioning, while conscious, but not including activity.  This accounts for most of your daily energy needs (~1200 kcals).  NEAT refers to all the low-level or general activities you may perform that don’t include deliberate acts of exercise or sports, such as chores, walking, fidgeting, errands, etc.  Lastly, TEF represents the energy demands of digestion, and these demands can change based on your food choices.  How much do each of these things contribute to your energy expenditure?

• BMR - ~60%
• TEF - ~10%
• NEAT (~20-30% if EA is low)
• EA (~20-30% if NEAT is low; you exercise, but are otherwise sedentary)

IMPORTANT CAVEATS:

• As you lose weight, your BMR decreases
• The longer you stay in a deficit or below your “bodyweight set-point”, the more your NEAT decreases
• Two people with identical genetics can demonstrate a difference in NEAT by up to 2000 kcals!

All of the above caveats make your “target calories” a moving target!  Embarking on a weight-loss journey without considering the marvel of your metabolism - which is designed to keep you alive in times of food scarcity - is possibly the greatest oversight in nutrition.  Now, despite all the underlying complexity of metabolism, the process of determining and narrowing down what YOUR calorie needs are is actually quite straightforward:

1. For 1-2 weeks gather the following data:
   1. daily bodyweight
   2. all foods eaten or drank daily
   3. daily activity (time, type, and intensity)
      1. "All foods" not only refers to the what, but specifically how much (e.g. 1 cup of cooked rice, 200g of raw chicken breast, etc.)
2. Use a reliable reference database for caloric values of common foods (e.g. USDA database, appendices of a nutrition textbook, MyFitnessPal, etc.) to calculate your daily caloric intake.
3. Is your weight decreasing, maintaining, or increasing?  Also take note whether the first 7 day average is within 100kcals or less as the last 7 days.  Generally, most people put on weight over the Fall/Winter holiday season.  In other words, you are likely maintaining weight on your current intake.
4. If maintaining, you are neither in a deficit nor a surplus for your CURRENT weight AND activity level.  Sometimes people's eating habits don't really change all that much from age 20 to age 30.  However, their activity level can reduce drastically upon leaving house league or varsity sports and entering a sedentary workplace.  People buy cars, start families, and ultimately begin to rely on the daily conveniences of fast-food, snack-foods, delivery options, and of-course... get-thin-quick schemes.
5. Now in order to lose fat, you must induce a caloric deficit, which if you'll recall has several moving parts: Calories-In & Calories-Out (and all its divisions).  So if you consume less calories but maintain your activity level and lifestyle, or conversely maintain calorie intake but become more active - a calorie deficit can be achieved.  Ideally, a combination of the two major determinants is best, however that may depend on the specific scenario. 

E.g. A previous client came to me with a markedly low-energy intake (according to the Harris-Benedict equation, she was already in a caloric deficit), yet was still 20-30lbs overweight.  The calories weren't adding up!  Clearly this meant the calorie model didn't fit!  YES!  CICO debunked! ..... or maybe something is being overlooked?  - what jumped out at me was her remarkably low-activity level.  SOLUTION: we kept her calorie intake where it was while increasing her protein intake moderately, but our ace-in-the-hole was getting her started with a progressive, resistance training program for home.  Without changing her calorie intake she lost over 20lbs and was her lightest since high school! 

So was this client actually in a caloric deficit when she came to me?  According to the equation, yes - according to real-life, NO!  By definition, because she was not losing weight she was NOT in a caloric deficit.  It's important to remember that equations are crude estimations of calorie needs, and just exactly how efficiently individuals digest and utilize/partition the food molecules they eat is unique to them.  Activities like resistance training stimulate muscle protein synthesis (MPS) to a large enough degree that we can actually see its effect in 1-2 months - which is pretty amazing to think about!  The food you eat literally forms the essential elements of contractile muscle!  Because we created a demand for protein and energy (in the molecular form of ATP), we robbed her adipose (fat cells) to maintain, build, and repair actively trained muscles.  Training created the deficit, but it also told her body what to do with her food: Burn the Fat, Feed the Muscle!

Do you have a good understanding of why your diet didn't work, or why it may have worked initially but you couldn't sustain it?  Millions of people diet, and dieting is a Billion dollar if not Trillion dollar industry.  The culture of body image and weight loss means big bucks for people looking to capitalize by marketing diet products and programs.
You've probably tried a few different diets and achieved similar results, or perhaps you experienced divergent results but a common regression to your original starting point - perhaps you ended up gaining more than you lost.  This is a common problem.  It's been said that we don't have trouble losing weight - people do it everyday.  Rather, we have trouble keeping weight off.  Why?

The reason....

Please watch, listen, and share the video lecture.

"I'm so unmotivated", "I need a new routine", "I need something different", "I got bored of my old program"...

Do these sentiments sound familiar?  I hear this stuff all the time, and it's one of the many things that drive me batty. 

I've been training for over 20 years, and I've been training others for just over a decade, so believe me when I tell you I've heard it all.  I know how the average person perceives exercise; I know their good habits and I know their bad habits; I know why most people start and stop exercising; I know the success and failure rates; I know what separates them from me.  I know this from experience, and I know this from the abundance of exercise physiology, psychology, behavioural, and epidemiological research.

There's always some new article or book that convinces people of the obscure missing piece to their daily regimen that will magically be the one thing that sends them over the top of whatever obstacle(s) have been keeping them back.  But I, as well as the scads of coaches who actually work with people one on one (not just write books or articles), know that those who fail to accomplish their goals, whether fitness-based or otherwise - do so because they neglect the fundamentals, the basics - not the nuances.

Fundamentals account for 90-95% of success, whereas nuances are largely unnecessary components of the bigger picture.  A machine can be "finely tuned", but it can nonetheless perform its job as directed without fine tuning.  Fine tuning just means it does the job with less wasted energy.  The irony when it comes to a goal like weight-loss is that wasted energy IS the goal.  The less efficient you are, the more energy you expend, and the more weight you lose.  In contrast, getting fitter is a process of becoming more efficient at a given task - whether physically (e.g. stronger muscles move weight easier), or physiologically (e.g. more and larger mitochondria and RBC's allow you to use oxygen more efficiently).  This is why, in part at least, you find it difficult to maintain your weight-loss momentum from month to month.  You've picked all the low-hanging fruit (the easy weight), and now you have to work a bit harder and/or longer to get more weight off.

If you have a fitness goal, which also accomplishes health goals by proxy, you only need to worry about doing the basics, repeatedly, over a long enough timeline to see your goals through, and with the intent of doing so as best you can while acknowledging that you can always improve:

1. Do not overfeed yourself - or starve yourself
2. Do not restrict or avoid foods or food groups
3. Be active, regularly - but not obsessively
4. Get enough sleep
5. Avoid "all-or-nothing" attitude towards life
6. Pay attention to what you are doing, and learn from your mistakes
7. Strive for excellence; do the best you can; do better over time

Do NOT worry about silly, dichotomous thinking and biohacking BS such as:

1. Should I eat all my carbs at the start of the day or at the end of the day?
2. Should I sleep all at once or take micro-naps through the day?
3. Should I eat low carb or low fat?
4. Should I go Vegan or Carnivore?
5. I should count every calorie...or...Calories don't count if I do this diet!
6. Tracking food is obsessive compulsive, so I'm going to intermittent fast instead and create a binge eating disorder - yay!
7. I should only do only the BEST exercises, otherwise exercise isn't worth doing!
8. I'm 44, overweight, poor diet, high BP, and no training experience or formal guidance in exercise.... time to start training for that marathon and eating only meal replacement shakes!
9. I need to eat only low-glycemic carbs, less than 25g at every other meal, across 10 meals per day, between the hours of 12pm and 8pm, paired with only lean or vegan protein, every other day on my rest days where I only do fasted, low-intensity steady-state cardio first thing after I wake up.  Unless I'm on a carb load refeed - in which case I eat only 2 meals per day, immediately after my workout if 1 hour or less, otherwise before my workout if 1 hour or more, at 1500 calories each, containing 200g of mixed carbs each meal, with fats as low as possible to speed up gastric emptying and maximally stimulate insulin to "drive nutrients into my cells", along with at least 0.1g per kg/bodyweight of leucine to stimulate muscle protein synthesis from a protein source that is either only lactose free, gluten free, egg-free, free-range, grass-fed, organic, and ethically butchered....unless it's Saturday - in which case YOLO!!!!!!!!

We need to stop this nonsense.  These examples are all indicative of behaviour that attempts to circumvent long term commitment to the process, in favour of an easier way to the prize.  There isn't one.  This is true in life, as well as fitness.  For this reason, I find it typical that those who fall for these shortcuts and empty promises of success without effort tend to display a similar kind of half-assed approach to their jobs and home life.  Your "new routine" should be seeing your current routine through to the end.  Are you bored with progress?  If you are bored it's because you're just going through the motions, and in the beginning that was enough to keep you interested.  If you're bored it's because you never identified what your goals were, and thus you don't know why you started your routine in the first place.  That or you need a reminder - progress is the goal, not entertainment.

How you do fitness, is how you do life, work, and family - "If you don't have time to do it right, when will you have time to do it over?" - John Wooden