True or False: You Can (Ab-)Use Nicotine Chewing Gums to Get Shredded Without Compromising Your Health

Nicotine gums are made for smokers. Smokers are leaner than no-smokers. Chewing nicotine gums helps you lean out... broscience? Logic? Or bullshit?

It's one of the better-known pieces of broscience: "Nicotine chewing gums will promote weight loss!" Aside from being "better-known", it's yet also highly controversial. In that, people usually don't question the fact that nicotine chewing gums may promote weight loss (we do all know that smokers, are leaner, don't we?), but rather that they do so in the absence of significant ill-health effects.

Since this is the SuppVersity and not the bb.com bulletin board, I am not going to restrict today's analysis on the health issues. Instead, I will start by looking for scientific evidence that would confirm the common sense assumption that chewing nicotine gums does in fact promote weight loss -- in humans, not in rodents (Lupien. 1988).
Let's first take a look at the connection between nicotine and body weight management in general. In 2006 Chen et al. published an intriguing paper the title of which could in fact explain why smokers tend to be lighter than non-smokers (for US citizens that's ~ 3.7% leaner; cf. Albanes. 1987): "Cigarette Smoke Exposure Reprograms the Hypothalamic Neuropeptide Y Axis to Promote Weight Loss" (Chen. 2006)

According to Chen et al., the anorexic effects they observed in a 4 week rodent study are behind the anti-obesity effects of smoking. Similar effects on appetite in general and reductions in sugar cravings (Grunberg. 1982) in human studies as well. Nevertheless, if a reduction in appetite was the only beneficial effect of nicotine would be limited to phases of ad-libitum dieting. A direct effect on fat loss, as it is implied by broscience, on the other hand, would not exist.
If it was not for Schechter et al. and other scientists who report "nicotine-induced weight loss in rats without an effect on appetite" (Schechter. 1976), I could stop here and tell you that (a) you obviously don't want to chew nicotine gums for the rest of your life to benefit from its appetite suppressing phases and that (b) it wouldn't make sense to chew them in a phase, where you're counting calories, anyway (if you want the appetite suppressing effects, anyway, add caffeine, this will enhance them; Jessen. 2005).

Figure 1: Body weight and food intake in 13 week rodent study with 0.4mg/kg and 0.8mg/kg (right) of nicotine administered in solution or saline control thrice daily (Schechter. 1976)

Thanks to the impressive reduction in body weight Schlechter et al. observed in the previously cited rodent study in the absence of statistically significant reductions in food intake (graphs at the bottom of Figure 1), it's worth to keep digging further.
If you take a close look at the results you will yet realize that there is a big caveat to the impressive weight loss (specifically in the 3x0.8mg/kg group | human equivalent ~ 3x4mg or three high dose nicotine chewing gums). Yes, I am talking about the the nasty weight regain that occurred - likewise in the absence of increased food intakes - when the nicotine administration was seized.

Against that background, it's all the more important to find evidence from human studies. Unfortunately, the majority of studies on nicotine gums is not relevant to the topic, because they are (a) dealing with the success of smoking cessations, or (b) dealing with weight regain after smoking cessation. We will therefore have to resort to ostensibly unrelated results such as...

• Figure 3: Plasma leptin levels in non-smokers, long-term nicotine gum users and smokers after adjustment for age and body composition (Eliasson. 1999)

  the increase in leptin levels researchers from the Sahlgrenska University Hospital in Göteborg (Sweden) observed in a 1999 study in 73 subjects: 23 non-smokers, 31 smokers and 19 long-term nicotine gum chewers (NGCs) with similar ranges of age, body mass index (BMI) and per cent body fat. As the authors of the corresponing paper point out, "[t]he increased leptin levels may be an important reason for the lower body weight in smokers." (Eliasson. 1999). Unfortunately "long-term" is nothing you would associate with the use of nicotine gums as diet adjuvant.
  
  As suggestive as they may be, the increases in leptin are thus probably not relevant for short term decreases in body weight - or even better body fat - as you would expect them, when you're dieting.
• the association with hyperinsulinemia and insulin resistance the same Swedish researchers from the Sahlgrenska University Hospital observed in a previous investigation (Taskinen. 1996) clearly suggest that the chronic consumption of nicotine leads to insulin resistance, metabolic abnormalities associated with the insulin resistance syndrome, and increased cardiovascular morbidity.
  
  On the other hand, we are - I can't repeat that often enough - not talking about the chronic use of nicotine gums, but their (ab-)use for 4-6 weeks to propel your fat loss results. Eventually, the results are thus as irrelevant as the previously mentioned beneficial effects on leptin (see previous bullet-point).

• Figure 4: Thermogenic effect in 150min after the ingestion of nicotine and / or caffeine (Jessen. 2003)

  the "pronounced" thermogenic effect researchers from the The Royal Veterinary and Agricultural University in Denmark observed in their 2003 study. Aside from scientific evidence that the administration of nicotine has thermogenic effects, the second important result of the study at hand is the observation hat the thermogenic effects  of 1 mg nicotine (measured over 150 min after the ingestion) can be (almost) doubled, if the nicotine is administered in conjunction with 100 mg of caffeine (Jessen. 2004).
  
  It's also important to note that "[i]ncreasing the nicotine dose to 2 mg does not increase the thermogenic effect but produces side effects in most subjects." (Jessen. 2003) More is thus, as so often, not better for nicotine (a similar non-linear dose-response effect was observed with cigarettes, as well; cf. Collins. 1996). A previous study by Collinset al. (1994) found a 7.5% increase in resting energy expenditure with 200mg of caffeine and a similarly low amount of nicotine, i.e. 0.8mg of nicotine from cigarette smoke over a 3h period.

If you take a look at the evidence I provided, it supports the previously raised concerns about the long-term use of nicotine gums. On the other hand, the study by Jessen et al., as well as the study Collins et al. who didn't just find a similar synergistic effect of caffeine and nicotine, but were also able to show that the effects occur in both smokers and non-smokers (Collins. 1994; similar results in Perkins. 1989), clearly indicate that the short-term (ab-)use of nicotine gums may in fact promote the loss of body weight and - assuming you're getting your 1.5g/kg protein and lifting heavy objects - body fat, as well.
Unfortunately, it is difficult to say whether these benefits come with significant negative effects on your health. Evidence on short-term effects of nicotine abuse in human beings is scarce. Furthermore studies in non-smokers suggest that healthy people and people with pre-existing problems with glucose management react differently, with the former experiencing no and the latter experiencing severe reductions in insulin resistance in response to the acute infusion of nicotine in a 2001 study by Axelsson et al.

Figure 6: Negative effects of nicotine on insulin sensitivity occur only in diabetics (Axelsson. 2001)

As far as the dreaded increases in insulin resistance are concerned, you could thus argue that the contemporary evidence suggest that healthy athletic individuals have nothing to fear. Since the same appears to be true for the negative effects on platelet count (Mundal. 1995), blood pressure and other markers of cardiovascular health (Benowitz. 2002). For people who belong to one of the classic risk groups, i.e. men and women with metabolic syndrome and / or existing heart condition, the use of nicotine gum may yet easily result in a hospital stay or worse (Rigotti. 1986).
References:

• Albanes, Demetrius, et al. "Associations between smoking and body weight in the US population: analysis of NHANES II." American Journal of Public Health 77.4 (1987): 439-444.
• Axelsson, T., et al. "Nicotine infusion acutely impairs insulin sensitivity in type 2 diabetic patients but not in healthy subjects." Journal of internal medicine 249.6 (2001): 539-544.
• Benowitz, Neal L., Anna Hansson, and Peyton Jacob. "Cardiovascular effects of nasal and transdermal nicotine and cigarette smoking." Hypertension 39.6 (2002): 1107-1112.
• Chen, Hui, et al. "Cigarette smoke exposure reprograms the hypothalamic neuropeptide Y axis to promote weight loss." American journal of respiratory and critical care medicine 173.11 (2006): 1248-1254.
• Collins, L. C., et al. "Effect of caffeine and/or cigarette smoking on resting energy expenditure." International journal of obesity and related metabolic disorders: journal of the International Association for the Study of Obesity 18.8 (1994): 551-556. 
• Collins, Lynell C., Jerome Walker, and Bryant A. Stamford. "Smoking multiple high-versus low-nicotine cigarettes: impact on resting energy expenditure." Metabolism 45.8 (1996): 923-926.
• Dallongeville, Jean, et al. "Cigarette smoking is associated with unhealthy patterns of nutrient intake: a meta-analysis." The Journal of nutrition 128.9 (1998): 1450-1457.
• Eliasson, Björn, and Ulf Smith. "Leptin levels in smokers and long‐term users of nicotine gum." European journal of clinical investigation 29.2 (1999): 145-152. 
• Etter, Jean-François. "Addiction to the nicotine gum in never smokers." BMC public health 7.1 (2007): 159.
• Grunberg, Neil E., Deborah J. Bowen, and Suzan E. Winders. "Effects of nicotine on body weight and food consumption in female rats." Psychopharmacology 90.1 (1986): 101-105.
• Grunberg, Neil E. "The effects of nicotine and cigarette smoking on food consumption and taste preferences." Addictive behaviors 7.4 (1982): 317-331.
• Grunberg, N. E., S. E. Winders, and K. A. Popp. "Sex differences in nicotine's effects on consummatory behavior and body weight in rats." Psychopharmacology 91.2 (1987): 221-225.
• Jessen, Anna B., Søren Toubro, and Arne Astrup. "Effect of chewing gum containing nicotine and caffeine on energy expenditure and substrate utilization in men." The American journal of clinical nutrition 77.6 (2003): 1442-1447.
• Jessen, A., et al. "The appetite‐suppressant effect of nicotine is enhanced by caffeine*." Diabetes, Obesity and Metabolism 7.4 (2005): 327-333. 
• Mundal, H. H., K. Gjesdal, and P. Hjemdahl. "Acute effects of low dose nicotine gum on platelet function in non-smoking hypertensive and normotensive men." European journal of clinical pharmacology 47.5 (1995): 411-416. 
• Lupien, John R., and George A. Bray. "Nicotine increases thermogenesis in brown adipose tissue in rats." Pharmacology Biochemistry and Behavior 29.1 (1988): 33-37.
• Perkins, Kenneth A., et al. "Metabolic effects of nicotine in smokers and non-smokers." Problems of Drug Dependence 1989 (1989): 469.
• Perkins, Kenneth A., Joan E. Sexton, and Amy DiMarco. "Acute thermogenic effects of nicotine and alcohol in healthy male and female smokers." Physiology & behavior 60.1 (1996): 305-309.
• Rigotti, Nancy A., and Kim A. Eagle. "Atrial fibrillation while chewing nicotine gum." Jama 255.8 (1986): 1018-1018.
• Schechter, Martin D., and Peter G. Cook. "Nicotine-induced weight loss in rats without an effect on appetite." European journal of pharmacology 38.1 (1976): 63-69.
• Taskinen, Marja-Riitta, and Ulf Smith. "Long-term use of nicotine gum is associated with hyperinsulinemia and insulin resistance." Circulation 94.5 (1996): 878-881.