Effectiveness of Cardio for Weight Loss

Effectiveness of Cardio for Weight Loss

Find out the truth about popular aerobic exercises before your breakfast, as deciding whether cardio is the most effective to burn fat is still a hot debate.

There are many athletes who believe this theory, and that’s why they run before breakfast on a daily basis. Sometimes, they also join local fasting exercise clubs, because they want to lose more fat. Is it really helpful to do aerobic exercises even before having your breakfast in the morning? Fasted cardio is an interesting subject, but answers about it aren’t so simple. It’s clear that any food equals to energy. For example, when people fast, their bodies use fat stores for morning exercises. It makes sense that the human body may not agree physiologically.

Basics of Fasted Cardio Theory

This infamous theory about fasted cardio was created in 1999. Basically, it indicates that the body can maximize its fat loss in a fasted regime during all kinds of aerobic exercises if they’re done before breakfast. This fasted cardio concept is quite popular, but it still remains controversial.

There’s an opinion that fasting decreasing glycogen and blood sugar levels in the body. Without the necessary energy from glycogen or carbohydrate sources, it starts turning stored fat into the fuel necessary for workouts. This theory also indicates that fasting for cardio exercises lowers people’s insulin levels, thus, increasing their fatty acid breakdown. This is what forces early bird bodybuilders and athletes to go to gyms in hope to achieve the best results for cardio efforts.

Is It Fact or Fiction?

Are feeling hungry during exercises and time lost sleeping worth your sacrifice? Is this a famous theory fact or fiction? To get the right answer to these and other relevant questions, it’s necessary to conduct some research. You also need to understand the process of fat loss itself.

To lose fat, your body needs to burn more calories, which are special units of energy stored in it and got from the food that you eat. Consuming more calories than your body can burn leads to weight gain, but exercises help you lose weight and burn more calories. Metabolism also plays an important role in how your body uses its energy for weight loss.

What about Research Findings?

The latest studies compared post-breakfast and fasted cardio routines and examined how they affected people’s metabolism, energy intake and appetite. The participants included 12 healthy and young men. There were many trials conducted over 10 hours for control, fasted and post-breakfast feedback. Men needed to perform fasted 1-hour treadmill runs upon walking for 1 trial, and they had to eat their breakfast 1 hour before their exercises the next day.
The results of these trials showed better appetite suppression if participants had their breakfast. Besides, there was no evident difference in the energy intake between fasted and post-breakfast routines, but both of them formed a negative energy balance, unlike a sedentary day. Conclusions claimed that running for 1 hour both fasted and after breakfast had the same calorie deficit. It’s clear that exercises create the necessary fat loss, when not fasting before them.

Results of Other Studies

Other studies examined the effect of breakfast on exercises. There were accurate records on post-breakfast appetite, metabolism and energy balance. Participants of these randomized studies included 12 physically active men, and they had to complete 4 trials, such as:

• Fasted workouts;
• Overnight fasting followed by rest with no breakfast;
• Breakfasts followed by exercises;
• Breakfasts followed by rest.

Furthermore, moderate intensity and continual running was used for a workout part, and its length was used on those men who rested instead of working out. They all consumed special test drinks 90 minutes after their rest or workout followed by lunch.

The results of these studies showed that glucose uptake is a bit faster in men eating breakfast with rest compared to men fasting with rest. However, there wasn’t any difference in participants exercising and resting without breakfast. Men who had their breakfast enjoyed increased appetite suppression during the day in all test categories. It’s amazing but the highest energy stores were recorded after lunch in the group that had breakfast followed by rest.

These studies also revealed less energy that remained in men who performed special fasted exercises. They also indicated that exercises were the main factor that caused a lowered energy balance, regardless of eating breakfast. Participants who didn’t eat it had a bit better results based on findings, while men who had breakfast showed their improved overall food cues during the day. It was also discovered that eating breakfast interferes with the appetite suppression given by fasted exercises.

This research is an excellent example of using fasted cardio exercises in different ways. You can get better appetite control after eating breakfast, which results in a lower daily calorie intake. Fat reduction and negative energy balance are provided by both eating breakfast and fasted cardio. When fasting, you can get a bit more positive results. It’s only up to you how you feel before regular exercises. For some people, waking up hungry and doing aerobic exercises may not be the best option. If you feel fine, it can work fine for you.

Further Findings

There were further studies on physically active males, and they examined aerobic exercises in fed and fasted states. 19 men took part in this research, and they were divided into 2 groups to compare their metabolism and body composition. 10 participants had their aerobic training in a fasted state, while others trained after having a meal.

This research lasted for 1 month, and all participants were tested on different occasions during this period.
According to the results of these studies, body fat was decreased in both fasted and fed groups. When it comes to a fasted group, its body loss percentage was higher only by 6%. However, its blood samples indicated decreased renal functioning and dehydration. This means that aerobic exercises in a fasted state reduce body weight and percentage of body fat, and eating before aerobic exercises is healthy. Fasted cardio is effective, but it’s not suitable for everyday lives of many people because of unusual circumstances.

Bonus Research

There were bonus studies on trained bodybuilders, and they were focused on evaluating their metabolism and body composition during Ramadan (no water or food during daylight hours). 16 bodybuilders took part in this research, and their trial lasted for 1 month (7 non-fasters and 9 Ramadan fasters). All male participants needed to continue their resistant training during this trial period. It’s interesting that body mass index and body mass increased by 2.5% in non-fasting men. Bodybuilders who fasted had no change in their BMI and body mass. Besides, weight resistance training proved to have no visible effect on their body composition and body mass. Fasting men suffered from decreased renal functioning and dehydration in the end.

Although this research isn’t cardio related, it gives a further insight into exercises and fasting. The only side effects of fasting during training include reduced renal functioning and dehydration, and body mass index and percentage don’t change. Some people may consider no changes in their body composition a good result, especially with fasting, as the main target of bodybuilding is increasing muscles and decreasing fat. Based on this research, there was no fat reduction in fasters.


Fasted cardio is always a personal decision, because doing exercises will give you fat loss, regardless of when you eat. The above-mentioned studies showed nothing superior about performing aerobic exercises on an empty stomach.

You should consider how you feel and pay attention to hunger and energy cues and do only those things that work best for your lifestyle and body.

Other Factors That Should Be Considered

The intensity of exercises is closely linked to fat loss, because working hard in a gym equals to burning fat, and this process requires enough energy. Longer training sessions require more energy, so intense workouts and fasted cardio over 1 hour may not be effective without a meal. You face a high risk of burning your muscles in a fasted state, as exercising on an empty stomach also increases protein breakdown that affects your muscle growth. You should burn fat while keeping lean mass.

EPOC, or exercise-post exercise oxygen consumption, is increased when people eat before their exercises. It’s your accelerated metabolism experienced for a few hour after exercises. All people lose their weight and burn fat differently. Something that works for your friends may not work for you, so exercise and eat smart.