In simple terms, an anorexigenic hormones (derived from Greek for an – “without” and oerxia for “appetite”) work by causing a loss of appetite, whereas orexigenic hormones stimulate it. These types of hormones are both vital when it comes to our health and over/under secretion results in a plethora of health problems. We’ll start this blog on metabolic hormones by taking a look at the anorexigenic hormone responsible for mediating energy expenditure and a major contributor in facilitating food intake and the levels of adiposity or fat mass, Leptin.
As with majority of hormones, it is carried through the bloodstream when stimulated and signals the hypothalamus to modulate caloric intake relative to current level of energy expenditure. Now this is not to say it’s only secreted now and again, most hormones are present in blood in little concentrations to control other physiological functions and maintain homeostasis.
Leptin directly regulates the level of body fat in human beings and support the notion that excess adipose tissue can be brought about via hormonal issues and not just bad diet. During fat loss caused by dieting, the level of leptin correspondingly goes down as does thyroid activity. Coincidentally, In recent years fasting has become popular with fitness professionals, but do they understand how it actually works?. During periods of fasting there is a rapid reduction of Leptin (however, could be related to reduced insulin concentrations through not eating) which results in a feedback mechanisms (hypothalamic modulators) which call for an increase in food intake that exceeds expenditure aka a period of overeating. Similarly, an increase in adiposity would result in an increase the plasma levels of leptin resulting in a state of negative energy balance when food intake would be less than that of expenditure.
So why is this an important consideration when dieting?
Because when using short term aggressive fat loss strategies the levels of leptin decrease rapidly with the overall fat mass. Sounds good so far, but this leads to increased appetite and extreme hunger as all the brain recognises is the signal identifying a period of starvation. This is where it becomes a motivational issue, if you've got a client or athlete you're training that is not fully motivated you're going to have problems. It's a slippery slope that results in elevated levels of almost all of the hypothalamic and leptin-regulated modulators that signal you to overeat, and quickly.
Now picture this stimulus to overeat and add into it the strict psychological barriers many coaches have imposed on foods. I’ve seen coaches diet plans that cut out whole groups of foods entirely and only have basic, bland, uninspired foods for up to a month. In conjunction with the stress of training, it’s not probably going to end well, especially when we're told what we can and can’t have or what is labelled as bad or good. It creates a binge mentality which we see all the time in the fitness industry, how many people on facebook or Instagram have you seen lose a load of weight, get loads of nice comments and likes and they proceed to go on a binge for few weeks of drinking and eating and end up back at square one? Or do you see someone reward a few hard days work with a entire "cheat day". You can thank Leptin and basic restrictive psychology for that one….
From the studies done on leptin, we can theorise that It supports the hypothesis that negative energy balance or catabolism cannot be maintained for long periods without satiety, hunger, compliance, and sustainability being questioned. I've said it in many blogs before, you shouldn't sit in a dietary deficit for longer than 4-5 weeks max without coming back up to your maintenance levels, this isn't just for your psychological benefit, but metabolically significant. Leptin is also stimulated by carbohydrate intake, so it would also suggest that omitting or reducing carbohydrate intake long term would also negatively influence satiety signals. Another reason why low carb diets do not work for a lot of people or work for a short period of time (see above example for the binging response brought about by rapid weight loss). It’s a fundamental misunderstanding of the human body and how it works, what works for one person doesn’t work for another and when your changing your diet, you’re not just changing your caloric intake, you’re inducing changes in hormone secretion and availability and biochemical reactions. There are biological barriers in place for a reason and it’s a reason I’ll always push a gradual reduction in foods and have issue with “shredding” diets which impose a huge caloric deficit promoting short term loss but ironically long-term gain in weight.
Next time..Leptin Resistance
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