What Prevents Us From Losing Weight?

One of the biggest failures of the diet and nutritional science worlds is the inability to help people lose weight and keep it off. 

"Treatment of obesity by reducing calorie intake, despite having a good success rate in promoting initial weight-loss, has a generally poor outcome for long-term weight control [7]." (McNay, 2013)

I recently came across McNay 2013, a fascinating study that looks at how this happens (in mice, but seems quite relevant!): "High fat diet causes rebound weight gain."

They used a fairly standard "high-fat diet" (HFD) to induce obesity in mice. The fats in the diet were lard and soybean oil, the usual suspects.

A very busy chart. From (McNay 2013)
Fig. 1 a and b. (AL = ad libitum)

What's interesting is that they then attempted to cure the obesity they had caused, using a variety of approaches: a high-carb diet (HCD), a high-protein diet (HPD), and a ketogenic diet (KD), and calorie restriction (CR)—a "diet" of the eat less variety.

CR worked best, regardless of the composition of the diet—they were under-eating by 30%, and that's easy to do to a mouse in a cage. However, this had a negative effect on the mice's brain.

The other diets also worked for weight reduction, in the order of KD best, then HCD, then HPD. The HFD mice stayed fat (Fig. 1a). For final weight of the mice allowed to eat to their heart's content, they KD also worked best, then the control, the HPD, the HCD, and the HFD was the worst (Fig. 1b).

The HFD also had a negative effect on the brains of the mice, regardless of how much they were eating. This effect also persisted to a small extent even when the mice were switched to one of the other, weight-loss-inducing diets.

However, once the CR mice were again allowed to eat as much as they pleased on their diets:

"As expected, all mice showed significant rebound weight gain after release from CR... However, rebound BW [body weight] was significantly different across treatment groups with obese mice treated with HFD-CR rebounding to a higher BW than controls.... Although DIO [diet-induced obesity] mice treated with non-HFD showed a trend towards higher  rebound BW than controls, this only reached statistical significance at a one point in the case of HCD.... Hence the failure to achieve long-term weight control following CR only occurred in obese mice fed HFD during CR, coinciding with the maintenance of altered hypothalamic remodelling."

So the damage to their brain from the HFD persisted even though weight-loss due to dieting (CR).

However, "The increase in rebound BW in DIO mice treated with HFD-CR was not permanent but resolved after 6 weeks of ad-lib chow re-feeding."

Now the HFD wasn't actually the high-fat diet, here, that's a bit of a misnomer. It was 45 % energy. The KD was 93.4 % energy from fat—that's a high-fat diet!

"It is of particular interest that the specific effect of moderately high fat diet  (HFD) to alter hypothalamic proliferative remodelling is not shared by ultra high fat ketogenic diet (KD)."

So fat alone isn't the problem. It's the combination of fat and carbohydrate, and a good dose in seed oils (provided here from lard and soybean oil), as has been shown in other studies. In other words, the diet we are told to eat by the dietary guidelines.

And the "eat less" advice we constantly hear doesn't work at all, unless you also change your diet.

"These data support the view that treating obesity with CR does not by itself cure obesity despite treating the overt symptom of increased BW."

(My colleague Peter at the Hyperlipid blog also had some thoughts on this paper.)

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Dobromylskyj, P. (2021, May 19). Of mice and men (2) In the brain [Blog]. Hyperlipid. http://high-fat-nutrition.blogspot.com/2021/05/of-mice-and-men-2-in-brain.html

 
McNay, D. E. G., & Speakman, J. R. (2013). High fat diet causes rebound weight gain. Molecular Metabolism, 2(2), 103–108. https://doi.org/10.1016/j.molmet.2012.10.003