What you're talking about is somatotype and it was dismissed as quackery back in the 1950s.
Yes, thyroid conditions will play a major role in your body composition, but among people with healthy thyroids (and no other diagnosable, treatable disorders) you still see about the same incidence of both obesity and people who are underweight.
The biggest predictors of obesity and the things we can address in order to fix obesity are lean body mass, caloric intake, and nutrient type/timing. I'm tempted to talk about all of these at length, but that would make this a VERY long post. I'll give you guys the short version and this will still be a horrifically long post. For those wondering about my qualifications to speak about this stuff with some authority, I'm a top tier personal trainer at what is quite probably the best gym in the world. With that, let's dive in...Lean body mass.
Lean body mass is tremendously important to your overall health. When we talk about lean body mass we're really talking about the quantity and quality of skeletal muscle. Obviously there are secondary considerations when we talk about muscle (flexibility, relative muscle balance/posture, activation and patterning) but when we talk about body weight/composition it's simple: more is better, and a base line amount is tremendously important.
When people talk about their metabolism slowing down as they get older what they are talking about is sarcopenia; the loss of muscle mass with aging starting after about 25. Without addressing it, AVERAGE people lose up to about 1% of their skeletal muscle mass every year. Sedentary people lose even more. In addition to the loss of muscle you see decreases in capillary density in your muscles. This means that your RESTING metabolism (how much energy your body consumes when at rest) goes down and your ability to burn calories through exercise is greatly diminished. Simply put, without lean muscle that time on the treadmill or lifting weights won't give you the same caloric burn.
This is particularly a problem since our bodies (pick one: did not evolve//were not designed) to function without a certain requisite basal metabolic rate. When your BMR drops below this point because of unchecked sarcopenia your overall metabolic pathways start getting properly fucked. We're talking about the loss of the T-cells responsible for breaking down fat in the first place.
This is why some form of strength training is incredibly important if you want to live a long, healthy life. It's also the first step to losing weight if you are obese without an underlying medical cause like hypothyroidism.Caloric Intake
By and large, at the end of the day calories in - calories burnt = change in body mass. This is almost perfectly true in the absence of major diagnosable medical disorders. Eat less and your body pulls the excess calories from existing tissue. If you diet, you will lose weight. However, this point ties into both the point before it and the point after it, mainly the point after it, and in the end there is a lot more to nutrition.
First, it's important to understand that change in diet will produce short term
results. If your BMR is too low because you lack the baseline requisite lean muscle mass you will find you regain the weight pretty fast once you resume eating comfortable amounts of food. This will not happen if you bring your lean body mass up and your overall % body composition to within acceptable limits.
As you diet, there are a LOT of things to consider, most of which I'll cover in our third point. One important fact is that it doesn't just matter how many calories you eat but where those calories come from. Metabolic pathways are tricky, complex beasts that are deeply inter-meshed with our endocrine systems. This is the most important thing that you need to know, though:
The body CANNOT burn fat in the absence of carbohydrates. "Fat burns in a sugar flame"; technically it's a metabolic process driven by oxidative glycolosis, but without glycogen (carbs) that process can not happen. If you don't have glycogen stored in your muscles or liver and you don't have any glucose in your blood stream from eating carbs your body has to MAKE the glucose to burn the fat it already has. It does this by breaking down protein. It pulls some of this protein from your muscles. If you don't have enough dietary protein it pulls even more protein from your muscles. Either way this is VERY BAD because as I mentioned, muscle mass is paramount.
To prevent this you need to continue to eat some amount of carbohydrates while dieting. That being said, by and large I'm not talking about what most people call "carbs". White bread is the worst fucking thing ever made. Vegetables are some of the best. What we're talking about here is glycemic index (GI); how quickly the sugars from your food enters your blood stream. Google is your friend. Low GI is good. High GI is bad. More on that later. Bottom line though, never cut carbs out entirely or you're shooting yourself in the foot. That's why the major fasting diets use juice cleanses. Small amounts of carbs constantly trickled in to fuel the fat burning process. This isn't the only way to do it, but it's an important concept to keep in mind.Nutrition type/timing
Okay, this one is the most complicated and also the most important. There are a few major takeaways that I make sure every one of my client understands. Without these, you will hate trying to lose (or gain) weight and feel terrible the entire time you are doing it.
To understand these points, you need to understand your body's limitations and how it (pick one: evolved//was designed).
- We were not meant to eat food only three times a day.
- We were not meant to eat food without expending effort.
- We were not meant to eat food that is seriously the nutritional equivalent of rocket fuel.
Our bodies are intended for a world where food is the limiting factor on lifespan and population caps. Hard work is supposed to equate to more food and our bodies are remarkably talented at dealing with periods when things go wrong and that hard work doesn't pay off. We are very, very good at getting fat when things are going well so that the second something is wrong we still have energy available. That used to be essential to our survival. Essentially your body can exist either in a healthy steady state or a turbulent feast/famine cycle. The latter leaves you feeling like shit, and you feel even worse if the "famine" portion never comes.
1) If you go 4-6 hours without eating anything your body's cortisol levels start to rise. This is the main stress hormone we produce. Our bodies literally feel stressed when, from our body's point of view, food isn't readily available. These elevated cortisol levels in turn trigger an insulin response when we do eat. Your body will rush and try to make fat as a result. This is the feast/famine cycle I mentioned. Solution: Eat more often. Snack regularly. Don't eat more, but spread out your consumption to avoid large periods of time when you don't eat. If you do go a long period of time without eating take steps to mitigate the inevitable insulin response. "Set off the trap" by eating something small with a very low GI. Or follow my advice from the second point and do some small amount of exercise before breakfast.
2) What your body does with the food you eat largely depends on what you did prior to eating it. Once upon a time we'd only get to eat if we walked around gathering berries or tackled a god damned antelope. Doing any kind of exercise primes your body to take the food you eat and do good, useful things with it (put it in glycogen storage) as opposed to bad things with it (making fat). Clearly if we don't need to work hard for the food there's tons of it around and now is the time to make fat so that we're ready for the lean times, right? As far as our bodies are concerned, this is true. As a result, the best time to eat anything is 30 minutes after you finish exercising. This is ESPECIALLY important if you continue to eat foods with a high GI as your body will be more successful in turning them into fat if it goes that route. If instead you exercise first not only will your body be less predisposed to making fat you will actually experience what's called glycogen supercompensation. The short of it? You have more glycogen available to your muscles, organs, and even your brain. You feel more alert, more energetic, and perform better even at mental tasks. It's kind of a big deal.
3) This one is all down to glycemic index. Seriously? White bread is the worst thing in the world for your body. I mentioned GI in both of my other points, but it deserves its own point because it's a REALLY big deal. The more you stay away from foods with a high GI and eat foods with a lower GI the happier you'll be and the more balanced you feel as you try to lose weight. If you must eat foods with a high GI be mindful of when you do it and consider that in relation to points 1 and 2.
Okay. This is long and rambling, but I think I got the basics across well enough. If anyone has any specific questions for me, I'd be happy to clarify anything that's weirdly worded or seems off.