I have been screaming about this for a year straight now. Any diet that restricts calories will reduce metabolic rate. This is not even debatable at this point in my eyes. The bigger thing now to show is that not only does it lower metabolic rate and that makes it not work long term but now I have found that it reduces thyroid function to accomplish this and we have know this for some time. Why are people still promoting this. The science on this is solid and clear. I am about to show you.
We have the already seen one very definitive study on the most well know example of caloric restriction. The Biggest loser. The NIH did a 6 year follow up of the contestants and it was clearly demonstrated that they all had a dramatic reduction in metabolic rate after 6 years. It was also well documented that they all gained the majority of the weight back despite still doing a pile of exercise and eating a caloric restricted diet. They gained the weight back because once you have decreased metabolic rate and you follow the calories in and calories out model, if you even eat slightly more than the impossibly low amount of calories you were using to lose weight, you gain weight again. It is a system built to fail.
Now we have to look at how the body lowers metabolic rate. What controls metabolic rate? Thyroid hormones!!!! I am about to lay out multiple studies for you that show that caloric restriction not only lowers thyroid levels and increases Reverse T3 levels, which block active thyroid hormone receptors so the hormone can’t get into cells, but that we have known this as fact for some time and that we know that this is how the body conserves energy to avoid death from starvation. How this cannot infuriate you is beyond me. Yet more evidence that we know that the eat less move more movement is harmfull and yet it is still pushed as the gold standard.
This first study is one looking at iodine supplementation to see if it will help reduce the effect of caloric restriction on thyroid function. The first line from the study:
“It is well recognized that starvation and malnutrition are associated with a low-T3 syndrome in man.”
It is well known??? To who? Not anyone that I have ever spoken to.
They continue on to say that the same effect has been seen in hypocaloric carb restricted diets. Well duh. Caloric restriction is the same no matter what macros you cut to do it. 800 calories is starvation no matter where that energy comes from. What their point is here I am unsure. Just another way to dig at carb restriction I guess.
So the end result of the study was that, of course, the 800 calorie diet killed thyroid function but also that iodine had no effect on the most important of results.
“The intake of the hypocaloric low carbohydrate diet resulted in a striking decrease in both total and free T3 and an increase of rT3 irrespective of iodine supplementation. T4 and fT4 were not affected in either group.”
This next one also states it as fact that caloric restriction lowers thyroid function and that fasting does this even faster. They also show it as a function of reducing energy expenditure to save lean mass. They go into more depth on the mechanism behind what causes it even. When they genetically modify mice to not be receptive to the CAR receptor that seems to control the lowering of thyroid levels and calorically restrict them they do not see a reduction in thyroid function and the lose significantly more weight than in the non altered mice on the same calorie restricted diet.
This clearly shows that if we can maintain out metabolism we will lose weight faster. This is the reason I make people eat to TDEE and then if we want to move weight faster we can play with short bursts of other strategies but the main goal is to maintain metabolism or weight loss stops.
This study shows yet again that caloric restriction lowers thyroid function but also that zinc deficiency can have a similar impact regardless of restriction or not. Imagine now if you are both zinc deficient and restricting calories which I am sure many are.
They took rats and starved one group but had their zinc levels correct and another group that were adequately fed and found that both groups had significantly reduced thyroid hormone levels.
This one actually shoots holes in the ketogains theory that as long as you get adequate protein you will be fine to caloric restrict.
They took humans and divided them into groups of either calorie restricted, sedentary eating at maintenance or exercising and eating at maintenance. They ensured the calorie restricted group was getting adequate protein and all other micronutrients as compared to the other groups.
Calorie restricted group had an average caloric intake of 1,779 calories.
Sedentary maintenance group had an average intake of 2,433 calories.
Exercising group had an average intake of 2,811 calories.
The end result was that the only group to have reduced serum levels of the active Thyroid hormone was the calorie restricted group. End of story there. How can we debate this?
Finally I want to stress that the only thing worse for thyroid function than restricting calories is fasting. I wrote this piece the other day about a doctor who showed his blood work after a week of fasting and it was blatantly clear that he tanked not only his thyroid function but also his testosterone. This is not healthy and the number one reason I tell people not to fast. Any weight you do lose in fasting is going to be only water weight and will only serve to further damage your hormones. It is not worth it.
There are actually plenty more of the same thing that are available to anyone that searches yet this is not something we ever hear about. Thyroid issues are such a huge issue today and it is pretty clear to me that the dieting industry that is dominated by caloric restriction is the reason. It is not a coincidence that the vast majority of people with this issue are women who have dieted most of their life. What more do we need to say about this? Why when the evidence is so clear and so easy to find that no one is talking about this and everyone, even the keto community as a whole, is still stressing that eating less is the way to go.
This is why I hate it that the keto community is hung on the idea that your hunger going away so you can eat less is such a great benefit. It isn’t. If as a community we truly believe that it is not about calories and that insulin is the driving factor then we need to stop with all this eat less bullshit. We need to fuel our bodies to make them work. Stop starving and start thriving. Feed your Thyroid.
If you want to get your thyroid function back as well as your total health but still want to lose weight I can help.
I currently have openings for personal coaching. Come join the thousands of others I have helped to get their health back and start losing again.
Check the details here: