The low carb/keto followers have gone as far as to say that you can gain fat while in a caloric deficit if you are eating carbohydrates because insulin drives obesity, not calories.

This rotates around the carbohydrate-insulin theory of obesity whereby insulin (a hormone that helps shuttle glucose into cells) is proposed to drive fat gain and obesity due to its inhibition of lipolysis and fat oxidation.

If insulin truly had that powerful of an effect and caused people to gain fat, then it must be somehow affecting one of the components of TDEE, thereby lowering your daily TDEE and thus creating a caloric surplus, and tilting energy balance towards storage.

The idea that eating carbs can cause you to gain fat even if you are in a deficit is a completely false claim. If eating any amount of carbs cause you to gain fat regardless of your caloric intake, that would mean that carbs must somehow cause your BMR, NEAT, or EA to go into the tank. The data does not support this claim in any way.

I’d like to point out that the carbohydrate-insulin model of weight gain and weight loss has been disproven several times over by several labs.*1*2*3*4*5*6

I want to be very clear on this point: it is impossible to gain weight in a caloric deficit. If you gained weight, then by definition you were not in a deficit.

When people say things like, “I ate in a deficit and gained weight,” this probably means they calculated using an equation that didn’t provide them with the correct deficit.

This doesn’t mean CICO (Calories in vs Calories out) is untrue; it just likely means that they are an outlier (mostly underreporting the calories) and probably have a slower-than-normal metabolic rate that an equation couldn’t predict.

The idea that the type of calories is more important than the number of calories you consume is simply untrue and has been shown through several research studies.

However, that isn’t to say that the types of calories you consume don’t matter at all; they do. Eg: highly Processed foods like bakery items and sugar syrups react very differently from Whole Natural foods.

A plethora of studies has demonstrated increased weight/fat loss and energy expenditure with diets that are higher in protein.*7*8*9*10*11

This is not entirely unexpected when you consider the TEF (Thermic effect of Food) for protein versus carbohydrates and fats. The TEF for protein is approximately 20-30% whereas carbohydrates are approximately 5-10%, and fats are 0-3%.*12

There have been numerous theories as to why protein is such an inefficient nutrient compared to carbohydrates or fat, but it’s likely due to the effect of dietary protein on overall protein turnover.

You see, when sufficient protein is ingested, it increases muscle protein turnover and muscle protein synthesis.*13 Muscle protein turnover is an ATP-requiring, energetically expensive process and may increase the usage of ATP and thermogenesis.*14

Dietary protein also improves the retention of lean body mass during caloric restriction, meaning more fat loss and less lean mass loss.*15 This may help maintain metabolic rate better and assist in limiting body fat regain post-diet.

Not only does the protein content of the diet seems to impact TEF and fat loss, but fiber also appears to have a similar effect on reducing body weight when substituted calorie for calorie with non-fiber carbohydrate.*16

This is likely due to a portion of fiber being non-metabolizable, which would effectively reduce its “net” calorie contribution since some of the fiber calories are “wasted” during digestion and assimilation.

Both protein and fiber are also beneficial because they are very satiating. In fact, if calories, protein, and fiber are correlated, the effect of the ratio of carbohydrates to fat appears to have zero influence on fat loss.

Based on the research data I have presented here, two things are very evident. The first is not all sources of calories are created equal meaning they don’t all produce equal weight gain or loss depending upon the macronutrient breakdown of different diets.

The second is that the quantity of calories you consume still matters more than the source of calories you consume. TEF, while important, is still only about 15% of TDEE, so you can’t just eat as much protein as you want and lose weight.

If you consume 1000 calories from protein, you are going to dissipate around 300, but you will also retain 700. Now, that’s better than 1000 calories from fat, which is at best around 30 kcal dissipated, with 970 kcal being retained.

How much does this matter in reality? If you were on a diet of 2000 kcal per day with

400 kcals from protein,

800 kcal from carbohydrates,

and 800 kcal from fat,

then you should end up with a net of 1796 kcal

based on the TEF of each (assuming a TEF of Protein-30%, Carb-7.5%, and Fat-3%, respectively).

If you doubled your protein to 200 grams per day

and got 800 kcal from protein,

600 kcal from carbohydrates,

and 600 kcal from fats,

then you would end up with a net of 1697.

So effectively, you should have reduced your “net” calories by about 100.

This is a nice benefit, but it hardly justifies gorging yourself on protein just because it’s more thermogenic. If we use our previous example of a person who increases their protein from 100 grams per day to 200 grams per day (800 kcal) but does not decrease their carbohydrate and fat intake (800 kcal from each) then we end up with a net calorie amount of 2,076.

If this person’s maintenance calories were 1900, for example, increasing their protein without decreasing their carbohydrate and fat intake to compensate would have actually led to weight gain.

This is why calorie intake does matter and is the most important overall determinant of weight and fat loss. This doesn’t mean that total calories are the only thing that matter; it just means they are the most important.

Still, others will attempt to discredit or question the CICO model by bringing up topics like thyroid hormone. I can’t tell you how many times someone has said that CICO doesn’t work for them because they have low thyroid hormone or some other condition.

While low thyroid hormone can certainly make it more difficult to lose weight due to reduced BMR(Basal Metabolic Rate), that does not negate CICO or energy balance. It simply means the “calories out” side of CICO is less than you would predict.

You see, any criticism or “gotcha” critique of the CICO model is simply hand-waving to confuse you to believe in magic.

However, energy balance and CICO are not “opinions” or “discussions” any more than the earth being round is a discussion.

Someone may have a lower or higher BMR that doesn’t fit with energy expenditure equations, but that doesn’t invalidate CICO anymore than an inaccurate thermometer invalidates the existence of heat.

Hopefully, I’ve convinced you that CICO/energy balance is a viable model of weight loss/gain. Understanding how energy balance works is critical to understanding the blogs to come.

Now we’re ready to dive deep into the physiological and psychological mechanisms behind why diets fail.

*1 (2016, July 6). Energy expenditure and body composition changes after … – NCBI – NIH. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/27385608

*2 (2018, July 9). Efficacy of ketogenic diet on body composition during … – NCBI – NIH. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6038311/

*3 (2017, February 20). Impact of a 6-week non-energy-restricted ketogenic diet … – NCBI – NIH. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5319032/

*4 (2015, August 13). Calorie for calorie, dietary fat restriction results in more … – NCBI – NIH. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4603544/

*5 (n.d.). Ketogenic low-carbohydrate diets have no metabolic … – NCBI. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/16685046

*6 (2017, February 11). Obesity Energetics: Body Weight Regulation and the Effects of Diet …. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/28193517

*7 (n.d.). Protein quantity and quality at levels above the RDA improves adult …. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/15640518

*8 (n.d.). Dietary protein and exercise have additive effects on body … – NCBI. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/16046715

*9 (2009, January 21). Moderate-Protein Diet Produces Sustained Weight Loss and Long …. Retrieved August 21, 2018, from https://academic.oup.com/jn/article/139/3/514/4670368

*10 (2017, June 8). A High-Protein Diet Reduces Weight Gain, Decreases Food … – MDPI. Retrieved August 21, 2018, from http://www.mdpi.com/2072-6643/9/6/587/pdf-vor

*11 (2014, February 6). Thermic effect of food, exercise, and total energy expenditure in … – NCBI. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/24589371

*12 (2004, August 18). Diet induced thermogenesis – NCBI – NIH. Retrieved August 21, 2018, from https:// www.ncbi.nlm.nih.gov/pmc/articles/PMC524030/

*13 (2012, July 20). Leucine content of dietary proteins is a determinant of postprandial …. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/22818257

*14 (2016, November 30). Meal Distribution of Dietary Protein and Leucine Influences … – NCBI. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/27903833

*15 (n.d.). effects of dietary protein on the composition of weight loss … – NCBI – NIH. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3629809/

*16 (2015, October 17). Effect of an isocaloric diet containing fiber-enriched flour … – NCBI – NIH. Retrieved August 21, 2018, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4639584/*