Insulin and Weight Gain
Contrary to popular opinion, there is no linear correlation between insulin and weight gain. Is is simplistic and generally wrong to just label insulin as the fat storage hormone, and put it in the bad category.
And yet, the majority of dieters are far more cautious about carbohydrates than overall calorie intake. Their fear is that along with carb consumption comes a spike in insulin levels, and hence the inability to lose fat.
Ironically, the same folks consume a copious amount of protein and amino acid supplements, which are insulinogenic as well, but this little detail seems not to matter.
Truth be told, mainstream nutritionists tie insulin and weight gain together because this hormone is the main regulator of lipoprotein lipase (LPL), which is still considered the key enzyme involved in fat storage.
However, research made it clear that animals bred without LPL can store fat just fine. This fact is ignored or not known, and most of these mediocre specialists still go on and on about insulin and weight gain.
They should probably get out of the 70's because their logic (insulin activates LPL + LPL stores fat = insulin stores fat) is totally outdated.
As it turns out, more relevant than LPL is acylation-stimulating protein (ASP), which turns out to be the most potent stimulator of triglyceride synthesis in the fat cell.
It's important to note than ASP doesn't necessarily need insulin to be activated. In fact, all studies showed that eating or infusing fat, even in the complete absence of insulin, will definitely stimulate fat storage.
I guess you don't expect to eat peanut butter all day long and stay lean. Or you do?
Contrary to popular belief, a higher insulin response to a meal doesn't mean a bigger appetite. In fact, numerous trials consistently found that a higher insulin response correlated with an increased feeling of fullness and decreased desire to eat. Remember when your mother was hiding the cookies before diner?
“Total ghrelin levels decreased significantly more after CHO or protein ingestion than after lipids, while ghrelin's nadir levels were reached most rapidly after the CHO-enriched preload.” (Koliaki et al., 2010)
Now, as a wise adult, you skip the cookies altogether because you fear that these high glycemic carbs would go directly in your belly fat.
In this case, you may want to know that whether you eat high or low glycemic index carbs doesn't make much of a difference in terms of weight gain/loss if calorie intake is controlled.
By corollary, if food consumption is not monitored, insulin secretion may indeed lead to weight gain because it plays an important role in modulating ghrelin concentration.
As a side note, ghrelin is probably the main hormone that regulates short-term appetite. So in other words, when you eat the cookies, insulin spikes, and conversely ghrelin drops along with your appetite.
However, the over-secretion of insulin will cause blood glucose to crash about an hour later, which means that ghrelin and appetite increase even above their previous levels.
So the easiest way to get fat, would be to keep eating junk food all day. But I'm sure you know that.
“The rapid removal of CHO from stomach should cause a rapid, strong suppression of ghrelin levels, an effect that might be short lived, because these nutrients are quickly absorbed and metabolized. “ (Koliaki et al., 2010)
With regards to weight loss, the majority of long term studies, lasting at least six months, showed that GI is not an important variable and can be neglected. (GI is closely correlated with insulin index.)
Nonetheless, at least one trial found that recommending a glycemic load in accordance with insulin resistance/sensitivity may lead to differences in weight loss.
In this vein, most short term studies (less than six months) show that lowering carbohydrate intake may give you a benefit in terms of weight loss.
In my opinion, this is due to the fact that the subjects used for these studies are obese and sedentary, and hence more prone to insulin resistance.
However, as they are dieting and insulin sensitivity gradually improves, the difference in carbohydrate intake seems to net out.
For this reason, most controlled studies whose duration approach one year show that low-carb diets don't have any weight loss advantage over their high-carb counterparts.
As a conclusion, while believing that insulin and weight gain are interrelated is just absurd (if calorie intake is kept constant), this hormone may influence the magnitude of the weight lost. But overstressing its importance is a mistake.
Many dieters can't see the forest for the trees and fail to realize that without a calorie deficit there is no way to get leaner, regardless of what they eat.
If you naively believe that eating lots of dietary fat is necessary for controlling insulin and weight gain, you're in for a big surprise.
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