Ask any person who has lost significant amounts of weight and he/she will tell you the weight comes off slower after the first 10 pounds or so. The initial weight loss is usually rapid and energy levels remain fairly high, but then it becomes more difficult to lose additional weight. Part of the reason for this common observation is a survival mechanism that kicks in when calories are restricted below maintenance levels to mimic a period of starvation. This process is termed “adaptive thermogenesis” in scientific circles and basically describes a process whereby calories are burned at a slower rate after a period of weight loss, making further weight loss more difficult.1-4
It is not hard to understand why this should happen in today’s society, when easy access to food and minimal work/ labor requirements make obesity one of the major health care issues. Yet, consider just a few generations ago, even as recently as the Great Depression of the 1930s, when food was scarce and labor-saving devices did not exist. Beyond those times, think of even harsher environments such as the trials of the pilgrims, the Great Potato famine in Ireland, the Dark Ages before the Renaissance, going all the way back to primitive man in his cave. Our bodies are genetically designed to store and preserve energy stores rather than wastefully burn calories when a spare tire develops around the midsection.5 The ability to gain fat has likely been genetically selected into our DNA code, as lean individuals who could not lower a fast metabolism during a famine probably died when the winter months came along or disease killed off animal herds.
Thus, the need for adaptive thermogenesis has always been present (at least until the invention of fast-food restaurants). Despite the value this biological response has in times of famine, it’s one of the main causes of failure for many dieters. Dieting is not a gratifying experience in the short term, so when the struggle and effort does not result in a tangible reward, many dieters lose motivation and give up. The shame of this emotional surrender is that time is on the dieter’s side, if he/she continues to stick to a mildly hypocaloric (500 calories/day under maintenance) diet with 30 minutes of structured activity.
Chemical Pollutants in Fat
Exactly why and how this metabolic slowdown occurs remains something of a mystery, but has been the subject of many studies. There are accepted observations, such as decreased thyroid hormone output and T4 to T3 (thyroid hormone) conversion, lower uncoupling rate in mitochondria, decreased activity, etc.1,6 There are also hypotheses that are more controversial, but intriguing when supporting data is presented.
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