Obesity is an increasingly global problem that is associated with a greater risk of developing disorders like hypertension and diabetes. Although dieting is an effective strategy, many people find it difficult to maintain and look for easier alternatives.
A popular alternative approach to effective weight management is supplementing therapeutic products that offer ‘fat-burning’ properties. These includes natural products and ‘functional foods’ that are claimed to suppress energy intake or actively increase energy expenditure. There are many commercial products that supposedly assist in effective weight management, including compounds like conjugated linoleic acid and pyruvate, as well as natural food products such as Irvingia gabonensis and chia seed. However, most studies on these products have been inconclusive (such as for Irvingia gabonensis) or shown that these dietary supplements do not assist weight loss (such as chia seed).
On a positive note, there is promising data on the anti-obesity effects of compounds called isohumulones, or iso-α-acids. These compounds are the major bitter components in beer and come from the female hop plant (Humulus lupulus L.). As shown in Figure 1, iso-α-acids are converted from α-acids during brewing, and impart flavour and bitterness to beer. These iso-α-acids have been shown to help obese individuals with pre-diabetes by reducing hyperglycemia and body fat content. In addition, iso-α-acids have also been shown to prevent diet-induced obesity in two different strains of mice. However, one drawback of using iso-α-acids is their very strong bitter profile, which makes them quite unpalatable at the concentrations required to be effective. Although an isohumulone pill would bypass these palatability issues, for reasons unknown, it has not been widely considered.
When beer is stored for long periods of time, there is a progressive breakdown of the iso-α-acids into more complex bitter compounds—known as matured hop bitter acids (MHBA). The MHBA compounds consist of oxidised derivatives that have similar structures to iso-α-acids but are less bitter and therefore offer a more palatable therapeutic agent. Recently, it has been shown that MHBA reduces body fat in rodents at least in part by increasing thermogenesis in brown adipose tissue. Brown adipose tissue is abundant in rodents and is important for their adaptation to cold environments. Adult humans have also been shown to have metabolically active brown adipose tissue, so this may be a possible target for anti-obesity therapies in humans.
The predominant source of bitterness in beer is from the α-acid compounds present in hops. These compounds break down into iso-α-acids during brewing and in isolation may provide benefits that reduce body fat in animals and humans.