Since there’s very little human data out there, I’ve been doing a bit of digging on differences in bingeing behavior between carbohydrate- and fat- fed rats. What I’ve managed to unearth is fairly striking. Rats appear eager to binge on any kind of diet, but this frightening fact is offset by the fact that only high carbohydrate diets induce addiction-like symptoms.
Rats are made binge eaters by offering them highly palatable foods for only short periods of time (approximately two hours) throughout the day. Regular lab chow is available for consumption the rest of the time. What we find is that rats binge on three kinds of foods: high sugar chow, high fat (vegetable oil) chow, or a combination of both sugar and fat in the chow. Rats that binge solely on sugar or solely on fat manage to maintain average body composition. Here, rats self-restrict and normalize after their bingeing periods, simply by eating less of the normal chow. However, rats with daily access to a sweet-fat mixture gain weight. This is what we witness with human beings. It lines up with our knowledge of insulin release and fat storage. Combining sugar and fat is the most insidious obesity-inducer of all.
High sugar rats:
Rats are made sugar addicts by being provided with laboratory chow 100 percent of the time, but for a short period of time, approximately 2-4 hours, provided access to sucrose solutions. When that sucrose window is removed from the rats’ daily routine, they demonstrate symptoms of opiate withdrawal. These include horrific behaviors such as paw tremor and violent head shaking. What worse, their symptoms and their frantic lever-pressing increases the longer they’ve gone without sugar. They also, when forced to abstain from sugar, demonstrate a 9 percent increase in alcohol intake, demonstrating cross-links in substance abuse. Sugar addiction can induce alcoholism. Fascinating and scary, huh?
High fat rats:
Some literature suggests, moreover, that similar patterns emerge with high fat binges. Teegarden and Bale demonstrated in one study that rats on both high fat, high carbohydrate, and mixed binge diets for 4 weeks, when removed from the diets, demonstrate severe anxiety and endure aversive environments to reach their preferred foods. They conclude that dietary withdraw and changed habits induces the rats’ stress state, which in turn induces “dietary relapse.” This data indicates that a stark change in eating habits, rather than the macronutrient ratios of the diet, is responsible for the extreme stress the rats display. Neurochemically, this makes sense as well. Both fat and sugar have strong effects on dopamine release, such that withdraw from a conditioned, pleasurable diet negatively effects the rats.
What we ultimately find, however, is that rats love fat, and do in fact binge on fat, but never experience symptoms of addiction or withdraw on a high fat diet. This lines up with my own experiences bingeing, and with those with whom I’ve conversed about fat binges. It is in fact totally possible, and totally satisfying, but not quite as demonic as sugar. The rats in this study were fed high fat diets, removed from the opportunity to binge, and then observed for addict-like behavior. None emerged. (!) They also showed no sign of opiate dependency. Moreover, most remarkable part, in my opinion, is that rats fed both a 100 percent fat diet and a 45 percent fat diet demonstrated no signs of addiction or withdraw. What we learn here is that fat has a neurochemical stabilizing effect on the brain. While definitely pleasurable to binge on fat, it is not what induces addiction symptoms. In rats. In humans, too, I’d bet. Loads.
Why do signs of opiate-like withdrawal emerge with sugar but not fat bingeing?
The relative lack of opiate-like withdrawal behavior after fat bingeing demonstrates the importance of opioid systems in differenetiating sugars and fats and their subsequent effects on behavior. Both sugar and fat effect dopamine signalling in similar ways, but opioids are another question entirely. You can read more about it here, but in brief: based on some recent data and neurochemical processes, it seems as though the lack of opiate-like withdrawal signs in fate-bingeing rats may be caused by fat-induced peptide activation, which can inhibit opioid transmission. In essence, fat likely interferes with opioid processes and effects in the brain.
The authors of this study conclude with the same caveat that I do. “Although we have not noted signs of opiate-like withdrawal in fat-bingeing rats, that does not mean that excessive fat intake cannot produce addictive-like behaviors. Withdrawal is not a necessary criterion for drug craving, just as food deprivation is not necessary for food craving.”
Sugar is the big demon here, but fat is not well understood, and it can still be a part of an unhealthy diet or disordered eating style. I have personally binged on just fat before (ever had 1000 plus calories of coconut? Pork Rinds? Macademia nuts? Bad. News. Bears.) I do know, and I do feel, the satiating effects of fat. I think about food far, far less when there is fat in my diet, and honestly, the types of cravings I feel now are orders of magnitude less than the cravings I felt on my 100 percent carbohydrate diet (can you believe I did that? Oh my god.) What’s more, keeping the carbs away, even ones as innocuous as vegetables, helps, too. Recall that the rats experienced the same phenomenon. Mixing sugar and fat was the worst combination for them, inducing both weight gain and symptoms of withdrawal.
It’s really nice to have this rat model, and to see our physiological responses validated. As complicated as our decisions and our lives are, we have comrades in mere rats, and we are all victims here. Cheer up, compadre! Eat some avocado and fuck the lollipops and we’re on the road! We’re not all the way there, to this destination of perfect mental and physical health, but we’re certainly walking and enjoying the stroll, which is all we could possibly ask for.