What the Research says about Intermittent Fasting (Part 2)
I’ve been busy researching, reading, and compiling more information from scientific studies done on intermittent fasting and its potential benefits. This is part two, but you can go here to read about more research on fasting or here if you’re not sure what intermittent fasting is all about.
Can intermittent fasting…
…improve blood sugars and prevent/manage diabetes?
- Animals that ate intermittently exhibited resistance to diabetes and improved blood glucose and insulin sensitivity, even if they did not achieve caloric restriction (Anson et al 2003; Duan et al 2003)
- Animals on daily caloric restriction have lower fasting blood glucose, fasting insulin, reduced inflammatory markers, and improved insulin sensitivity (Lane, Ingram, Roth 1999; Imai 2010; Hursting et al 2003; Lane et al 1995; Wang et al 2007; Bonkowski et al 2006; Okauchi et al 1995; Walford et al 1999; Walford et al 2002; Wang et al 2007; Kalani et al 2006)
- Human results on intermittent fasting are mixed:
- One study found no change in glucose but lower fasting insulin after 22 days of intermittent fasting (Hielbronn et al Jan 2005).
- One study found that, while fasting, subjects with diabetes had higher blood sugar levels (Saada et al 2010).
- Another found that after 22 days of intermittent fasting, women’s bodies showed more difficulty clearing blood glucose but that there was no difference in men. Men also had a decreased insulin response, but women didn’t. (Hielbronn et al Mar 2005).
- Another study found no change in glucose or insulin in men after 14 days of intermittent fasting (Halberg et al 2005).
- Two studies found that in humans, insulin sensitivity is more improved with fasting than with caloric restriction (Varady & Hellerstein 2007; Harvie et al 2010)
- Humans on caloric restriction showed lower fasting insulin levels, improved insulin sensitivity, and lower blood glucose. (Hielbronn et al 2006; Weiss et al 2006; Fontana et al 2004).
- The boiled-down verdict: Animals show improvements in blood glucose, insulin sensitivity, and resistance to diabetes with both intermittent fasting (without caloric restriction) as well as caloric restriction (without intermittent fasting). In humans, research on intermittent fasting and blood sugars delivers mixed messages, which probably means there are other factors involved that we don’t understand yet. There might be a gender difference in the blood glucose response to intermittent fasting. Several studies showed that daily caloric restriction can improve fasting insulin levels, insulin sensitivity, and blood glucose in humans.
- In one study, intermittent fasting reduced airway resistance, reduced inflammation, and improved the medicinal effects of albuterol in patients with asthma. (Johnson et al 2007)
- The boiled-down verdict: We need more research, but intermittent fasting may have some promising benefits for those with asthma.
…decrease risk of heart disease?
- In animals, caloric restriction has led to lower triglycerides, better cholesterol panels, and reduced inflammatory markers (Edwards et al 1998; Wang et al 2007; Kalani et al 2006; Lane, Ingram, Roth 1999).
- Animals on intermittent fasting and caloric restriction have lower blood pressures and heart rates (Tikoo et al 2007; Wan et al 2003; Lane, Ingram, Roth 1999; Wang et al 2007; Fontana et al 2004; Mager et al 2004).
- In humans, similar improvement is seen in cholesterol, inflammatory markers, and blood pressure with caloric restriction via intermittent fasting (Harvie et al 2011, Varady et al 2009; Walford et al 1999, Walford et al 2002).
- The boiled-down verdict: It seems you can protect your heart with lowered cholesterol, inflammation, and blood pressure by reducing calories, either by eating a little less every day or by intermittent fasting.
- Animals that eat intermittently exhibit slowed tumor growth, improved the effectiveness of chemotherapy, and reduced side effects of chemotherapy (Berrigan et al 2002;Lee at al 2012).
- In mice, intermittent fasting without caloric restriction reduced the occurrence and growth of lymphoma (Descamps et al 2005).
- Several studies show that animals with tumors had slower tumor growth and lived longer when calorically restricted with adequate protein, vitamin, and mineral intakes (Weindruch et al 1986; Pashko & Shwartz 1996; Pugh et al 1999; Imai 2010; Hursting et al 2003); however, one study showed mice had no slowing of tumor growth when on caloric restriction (Keenan et al 1997).
- Reviews of animal research conclude that the cancer prevention/slowing benefits are similar between intermittent fasting and calorie restriction (Varady & Hellerstein 2007).
- The boiled-down verdict: Research on the benefits of caloric restriction for cancer is mixed. Intermittent fasting may slow tumor growth and improve the effects of cancer treatment in animals. We need more research to know how these effects may transfer over to humans.