Rebecca Mastey's Blog

High insulin levels help you lose weight – at what cost?

I read an interesting study on the links between insulin levels and weight. The researchers suggest that a high insulin level is negatively associated with weight gain, which, in turn, suggests a high-glycemic diet is a benefit to those attempting to lose weight. I don’t have access to the full-text version, but the abstract alone left me scratching my head.

Reduced insulin secretion: an independent predictor of body weight gain

Relatively reduced insulin secretion, therefore, is a significant and independent predictor of the tendency to gain weight and adiposity in Pima Indians. The presence of relative insulin resistance also conferred an independent reduction in the risk of weight gain in some regression analyses. We conclude that insulin resistance and hyperinsulinemia are unlikely to play a causal role in the development of obesity, and that relatively reduced insulin secretion is a marker of an increased risk of weight gain in this population.

Without knowing the methodology of the study, it’s impossible to say how (if at all) the researchers controlled for the high rate – 50% + – of insulin-resistance among the Pima Indians. It’s also impossible to say if they found any causal or correlative relationship between the insulin-resistance and weight-loss, but failed to mention it in the abstract.

However, it’s clear that the researchers wanted to drive home the point that a high insulin-level conferred weight-loss, while a relatively reduced level was at least correlative to weight-gain. Let’s take a look at why this could be.

In an even cursory examination of the initial effects of Type II Diabetes, it’s obvious that a high-insulin level is correlative to weight-loss. Type II diabetics are insulin resistant – their cells do not respond to the insulin as do the cells of non-diabetics. In a normal individual, insulin drives the use and storage of circulating blood glucose, which results in blood glucose spikes and drops and, eventually, weight gain.

In a diabetic, though, the cells don’t respond to insulin. The circulating insulin can knock on the cell’s door all the day, demanding it take in the circulating glucose, but the cell won’t respond. This leads to incredibly high blood glucose levels and weight loss. Since the cells aren’t taking in the easily utilized glucose, they fall back on fat stores. The utilization of fat stores releases ketone bodies, which, in uncontrolled diabetics, results in ketoacidosis.

In another study that examines the relationship between weight gain and Type II diabetes, the researchers note the different responses to insulin among different ages. In the young, most studies conclude that high insulin levels are positively associated with weight gain. In the aged, many studies show, to one degree or another, a negative association between the two.

Obesity and Weight Gain Are Associated with Increased Incidence of Hyperinsulinemia in Non-Diabetic Men

On the contrary, higher levels of insulin predicted a gain in body weight and obesity in Pima Indian children [9] and in U.S. black and white young adults [12]. It has been suggested that hyperinsulinemia promotes weight gain in children and young adults, and that subsequent increase in insulin resistance and compensatory hyperinsulinemia then limits further weight gain in adults [9, 27].

The simplest explanation is that the young are not insulin-resistant and their cells respond to the call to store the glucose. As we age, we develop insulin-resistance and our cells are unable to utilize the circulating glucose. The former will result in weight gain, while the latter will result in weight loss.

If we’re solely concerned about achieving a healthy weight, then older individuals should aim for a higher insulin level. A high insulin level will encourage cells to stop responding to the insulin and utilize stored fat for energy. However, as the researchers note, high insulin levels come at a price.

These prospective population-based data emphasize the importance of avoiding obesity and weight gain during adulthood to prevent hyperinsulinemia [excessive insulin production] and, eventually, type 2 diabetes.

The high insulin levels may aid in short-term weight loss, but excessive insulin is a known precursor to diabetes. I’m still searching for the full text of the original study, and hope the researchers addressed this problem.

Fat’s not gonna kill you

Since the 1970s, Americans have been blasted with the “fat is lethal” mantra from doctors, nutrition experts, bureaucrats, Congressmen and the nosy old blue-haired lady at the grocery store. Finally, this nonsense might be coming to an end.

I won’t go into the long legacy of the fat=death kerfuffle (Gary Taubes does it well in the first section of his book Good Calories, Bad Calories). Needless to say, it’s messy and confusing and not scientific at all.

Recently, the Annals of Nutrition published the findings of an analysis of several relevant studies on the association between coronary heart disease (CHD) and fat intake. You can read the full report here, but here are a few highlights.

Intake of total fat was not significantly associated with CHD mortality [page 3 of 29]

Intake of TFA [trans fat] was strongly associated with CHD mortality [page 9 of 29]

Intake of SFA was not significantly associated with CHD mortality [page 9 of 29]

Intake of MUFA [monounsaturated fats] was not significantly associated with CHD mortality [page 9 of 29]

A 5% incremental increase in PUFA [polyunsaturated fats] intake was associated with a significantly lower risk of CHD events, but not with CHD mortality [page 9 of 29]

the lowfat diets did not affect CHD events [page 16 of 29]

Transfat is going to kill you. Polyunsaturated fats are going to save your heart. Later, in the discussion section

There is probably no direct relation between total fat intake and risk of CHD. The strongest evidence in support of this judgement comes from the Women’s Health Initiative that showed that CHD risk was not reduced after 8 years of a low-fat diet. The observational evidence, summarised in the meta-analysis, showed no association between total fat intake and CHD risk, although there was heterogeneity between the study results…

Clinical trials of fat-modified diets, in particular lowfat or high P/S diets, and coronary disease are rarely single factor interventions. Substitution of 1 type of fat for another or reducing total fat intake, invariably results in a range of food substitutions such that intake of other macro- and micronutrients is altered.

There’s a whole lot more in there that I could quote. It’s an amazing review that discusses one of the most life-altering mysteries of the 20th century. Dietary fat has been blamed for the ills of our time-from obesity to diabetes to depression-yet no study, to date, has provided a solid, causal relationship.The majority of studies supporting the dietary fat/ heart disease link, as this analysis states, involve confounding factors.

What these studies do succeed at, though, is the induction of the healthy patient syndrome. Just as the flu shot prevents 50% of deaths from all causes, study participants are so immersed in a culture of recording food that they naturally gravitate toward healthier eating. A reduction in fat may coincide with a reduction in refined sugar, high-fructose corn syrup, chemical additives, salt or any number of other potentially hazardous items. The suggestion to reduce fat intake may cause participants to seek out healthier alternatives, such as fresh fruits and vegetables. In essence, researches may be incidentally encouraging a “whole foods” diet, and the reduction heart disease recorded could, potentially, be attributed to a lower consumption of processed foods.

One of the major confounding factors involved in judging (accurately) the effects of “total dietary fat” on our health is the location of most of that fat. We’re more likely to take in the deadly fat/sugar combination through cookies, cakes and candies than take in large quantities of saturated fats from red meat. Perhaps it’s time we looked away from the fat, just for a moment, and turned our attention to our highly-refined, highly-processed food culture.