Hormones and Fat Loss


Appetite hormones are the hormones in our body that send signals to the brain to initiate feelings of hunger or fullness. These hormones play a big role in weight loss and weight gain—read below to find out more.

Ghrelin: Also known as the “hunger hormone,” ghrelin is responsible for stimulating your appetite to increase food intake and store more fat. During dieting and significant calorie deficits, the level of ghrelin in the body increases, which in turn increases food cravings and appetite. This is why we don’t want to significantly restrict calories or drastically reduce portion sizes, instead aiming for the F45 recommended amount of a 500-1000 calorie deficit per day for steady state weight loss.

Leptin: Also known as the “satiety/fullness hormone,” leptin is produced by adipose tissue, and its main roles include reducing appetite, regulating energy balance and maintaining body weight. A reduction in leptin levels occurs when you lose weight, which can cause an increase in appetite and inhibit weight loss efforts. In obese individuals, leptin levels are increased. This can cause leptin resistance, which means your brain will not receive the satiety signal and in turn excess calories may be consumed.

What behaviors affect my hunger hormones? 

Eat your meals slowly—it is actually really important! This allows our hormones time to be released in the gastrointestinal tract and signals to then travel to the brain, which actually takes around 20 minutes. Eating your meals too quickly can result in excess consumption, as our hormones do not have time to signal to your brain that you have had enough and are full, which is why you can go from starving to extremely full with no warning in between.

Sleep is another important factor when it comes to our hunger hormones. Studies have found that sleep deprivation is associated with higher ghrelin and lower leptin levels. Aim for 8 hours each night and turn off electronics at least 30 minutes before bed—this will help your brain switch off and allow you to fall to sleep.


Other important hormones for weight loss

There are other hormones that may also impact fat loss, the main one being cortisol.


Also known as the “stress hormone,” cortisol is released during times of stress or a “fight or flight” response. The main roles of this hormone include responding to danger or stress, helping reduce inflammation, increasing metabolism of glucose in the body, and controlling blood pressure. Cortisol levels generally return to normal once the stressful event is over, however, levels remain high in situations such as chronic stress and excessive exercise. This can increase our cravings for higher energy foods, such as refined carbohydrates, which can lead to weight gain or simply difficulty losing weight. Cortisol is naturally elevated in the morning and declines at night. When we are stressed and anxious, this balance of cortisol is in reverse, which is why you might feel tired throughout the day and wired at night. Balancing your nutritional intake with your training is an incredibly important strategy to managing your cortisol levels and succeeding in long-term fat loss. 


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