Newsflash: Newton’s first law of thermodynamics is, at best, only marginally useful when planning a diet.
Calories in vs. calories out is a simplistic model at best.
The macronutrient breakdown (carbs, fats, proteins) of your diet, as well as the timing of those nutrients, has a notable influence on how well you lose weight at a given calorie intake.
To start with, there is the obvious example of the Thermic Effect of Food (TEF) – the amount of energy necessary to digest and process the macronutrients you eat. For protein, it’s 20-25%. For carbohydrate, it’s about 10%. For fat, it’s 2-3%. What this means is that if you eat 2000 extra calories from protein, you’re only actually going to end up with 1500-1600 extra calories because of the metabolic cost to digest, absorb, and dispose of protein. If, on the other hand, you ate 2000 extra calories from fat, you’d end up with about 1950 extra calories after digestion, absorption, and disposal. That’s roughly an extra 400 calories or so that aren’t accounted for simply by counting the calories of foods you eat.
Then, there’s the example of hormonal differences. As discussed in a previous post (here), reducing carbohydrate intake below 120g per day decreases T3 (a thyroid hormone) levels in the body. T3 is an important regulator of metabolic rate. More T3 means a faster metabolism. So, eating 2000 calories including fewer than 120g of carbohydrate should result in fewer calories burned at rest than eating the same number of calories but swapping out some protein or fat to reach at least 120g of carbohydrate. When you’re planning a diet, you rarely account for swings in basal metabolism like that. (here’s the study referenced. Still can’t find full text, if someone wants to hook me up)
Finally, there’s the matter of energy storage. Your body can only store a certain amount of carbohydrate as glycogen. Past that point, it needs to store it as fat. So how efficiently can your body do that? Well, using this study as a reference, it’s only about 70% efficient. In this study, limited in size though it was, men were fed basically a crapton of carbohydrate – starting at 783g and building to 1059g per day. They ended up storing about 150g of fat (1350 calories) per day that they had converted from about 475g of carbohydrate (1900 calories). It’s no small deal when 550 calories per day just go “missing.” Other studies have corroborated this same basic idea in healthy, weight-training people – if you’re on a short-term all-out bulk, it may be a good idea to go REALLY high carb and low fat to gain lots of muscle quickly while minimizing fat gain.
So, all I’m getting at here is that even though “calories in vs. calories out” may be technically correct, all the contributing factors make the equation much thornier than most would assume to the point that, at the very least, being super anal about calories shouldn’t be your number one concern.
Which leads us to to the exciting part: people losing more fat and being more satiated with the SAME caloric intake because of nutrient timing. Also the confusing part: the beneficial effects were seen on almost opposite protocols!
This notion goes against the old-school conventional wisdom, but it has been popularized by the intermittent fasting crowd and the carb backloading crowd. Regardless of what you think about Martin Berkhan and John Keifer, the progenitors of these two eating trends, it’s neat to see a study (somewhat) verifying the efficacy of their methods.
The study was done on Israeli police officers, all of whom were obese at the start of the study. They all ate the same number of calories, but some ate the bulk of their carbs during the day, and some ate them at night. The result: the group that ate them at night lost 28% more fat, had increased satiety relative to baseline (even though they were on a calorie restricted diet!), had improved insulin sensitivity, saw a 44% increase in adiponectin, and had decreased inflammation – essentially outperforming in every single parameter the group that ate their carbs early in the day.
But before you head out to buy a quart of ice cream to polish off after dinner…
Ahh, verification of orthodoxy. In this study, obese women were fed 1400 calories a day. This included a 700 calorie breakfast, 500 calorie lunch, and 200 calorie dinner, or a 200 calorie breakfast, 500 calorie lunch, and 700 calorie dinner. The group eating half their daily calories at breakfast lost more weight and inches off their waist, saw larger decreases in fasting blood glucose and insulin, decreased triglyceride levels 33% (compared to a 15% increase in the group with a large supper), and experienced less hunger and greater satiety relative to the large supper group.
So, what sort of takeaway can we see here?
Well, for starters, don’t trust your body composition solely to Newton.
Second, some of the discrepancy may be explained by gender differences. Though not specified, more men than women tend to be police officers. The second study, on the other hand, was done exclusively on women.
Lastly, both studies were done on obese subjects. Whether these results will have any relevance to lean, active people is questionable.
Most importantly, I think what you should take away from this is that, if you aren’t satisfied with the results of your diet, don’t be afraid to play around with it. The solution to weight loss plateaus doesn’t always have to be simply dropping calories lower. Play around with when you eat your carbs, moving the bulk of your calories to one meal, trying carb/protein and fat/protein meals instead of mixed meals (or vice versa), moving more calories around your workout, running a higher surplus on training days and a larger deficit on rest days, etc.
Don’t be afraid to troubleshoot and experiment. There are a lot of factors in play when it comes to building an ideal diet for YOU as an individual, not just the boring old orthodoxy of calories in vs. calories out.