Just a note about metabolism and energy.
There are many factors, but one is always a major influence. Your thyroid controls your energy levels, metabolism and body temperature. Your metabolic rate influences your fat gain or burn. Without iodine we would all die. Iodine is essential as part of the thyroid hormones. Many are iodine deficient. While most countries have programs to provide iodine via iodized salt or through iodine in animal feed/fodder, often the program is inadequate or misses the individual. Most of the time I see problems with avoiding salt or using pink or sea salts that do not provide iodine. If you mid-afternoon oral body temperatures are less that 37C/98.6F that indicates a problem. If you want to know more …
With low thyroid function we see fat gain as the most obvious outcome.