If you ask someone in the general population what their fitness goals are, the overwhelming majority will answer something like: "I want to lose belly fat." If not belly fat, then usually the regions mentioned are the thighs or love handles.
Because that's what they feel most uncomfortable with, their goal is to lose fat in that particular spot. And when thinking about losing fat in a particular area, they believe they just need to work that region, which will cause localized fat loss. For example, if you want to get rid of belly fat, then doing a lot of crunches would help, as you're working that exact area.
This does have some reasoning behind it. There is evidence that spot lipolysis occurs to a greater degree in fat that is nearest to a contracting muscle (Stallknecht, 2017). Thus, one can argue that increased blood flow to a specific muscle might have an effect on fat loss. However, this study mentioned had 30 minutes of single-leg extensions. That's not 30 minutes where people are doing several sets of leg extensions; rather, it was a single set that lasted a half-hour (very light, of course). And the cardio lasted well over two hours. Therefore, we shouldn't put too much weight, if any, in said research when trying to apply it to the real world, where people do a few sets of leg extensions and then hop on the treadmill for 20 minutes.
How about direct studies looking into spot reduction? Many have done so, and in large, these studies have come out null. Although there is some nuance because many studies, both for spot reduction and against it, have important limitations. The biggest problem is that in many studies, the design was simply having a control condition of no exercise plus the group that trained a particular area. However, because the diet was uncontrolled, such studies frequently found that neither group lost fat, or sometimes one group lost fat and the other one did not. Neither is helpful to see if spot reduction occurs.
A study by di Palumbo et al. (2017) had 16 women training 3 days per week for 12 weeks. They had one group train resistance exercise for the upper body, and then aerobic exercise for the lower body. The other group did the opposite. Since aerobic exercise increases fat breakdown, it was hoped that spot reduction would occur. Neither group had a statistically significant change in body weight. However, there was significant fat loss nevertheless, which is what we care about.
What about spot reduction? For example, in the DEXA arm measurement, there was a 0.3 kg difference in the upper-body resistance training group compared to only a 0.1 kg difference in the lower-body one. A similar outcome in the legs occurred, although there was no difference in the trunk. The whole body measurement did not see any fat loss difference. The skinfold measurements also showed regional differences.
This does imply spot reduction occurred, but this study has some limitations. It was a small sample and researchers did not report P values for interactions. This is particularly problematic as many outcomes were measured, so the chance of having a difference increases if this isn't taken into account. The DEXA was also not the best choice of measurement and MRI should have been used. Some skepticism is recommended because other studies such as Löberbauer-Purer (2011) have shown the opposite, as we will cover.
This study had a larger sample size and four different groups: control, diet, diet and exercise, and diet with exercise plus a fancy exercise bike that enhances blood flow. The diet being controlled is especially useful, and fat loss did occur, which solves some problems from earlier studies. Unfortunately, DEXA was also used in the previous study. Exercise did improve the overall fat loss, but there were no regional differences, and even the exercise bike did not enhance spot reduction to a statistically significant degree.
This lines up with the overall trend of the evidence, but it is difficult to reference the many different studies done because each has many limitations that would make a very long and tedious article. But these two studies are good examples, one by its showing seemingly positive results but some reasons to be skeptical, and the other by showing that spot reduction did not occur even with a methodology carefully crafted to make that happen.
In the previous research that suggested spot lipolysis, even ignoring the limitations, the effect is incredibly small, amounting to a few grams of fat loss. It’s nothing that would be noticeable or relevant in a normal context. The Löberbauer-Purer (2011) study that we discussed also offered a subjective report of fat loss in addition to the normal measurements. Even though there was no spot reduction, some people felt the protocol allowed them to lose fat faster in their legs. In addition to research, one should also be skeptical of anecdotes claiming a person achieved spot reduction, as the placebo effect is clearly at play.
We don't recommend that people try to spot-reduce. It very likely cannot be done, or at least it cannot be done in a way that makes any practical difference. The place from which you lose body fat is largely based on your sex and individual genetics, and not something you can control. This is rather unfortunate, since people often feel like they are already very lean, except on a specific body part. However, there is no other option than simply continuing to diet. While the body has a set preference of where to lose body fat, it will eventually run out of places to get energy from. You will lose fat from that particular spot eventually, but it will take time.
It's also important to take the psychological aspect of this desire into account. While we certainly want people to become fitter, the obsession with fat in a particular place can become quite neurotic. In my experience, many people who are already lean and are worried about stubborn fat in a specific region look great as they are.
The area they are worried about is very frequently not as fat as they think, and in some cases, it starts to approximate body dysmorphia. If you want to lose fat in a particular area, by all means, continue to diet in order to achieve that, but also keep in mind that it may lead you to a rabbit hole of obsession that isn't worth the extra dieting and the psychological burden on your well-being.
Stallknecht, B., Dela, F., & Helge, J. W. (2007). Are blood flow and lipolysis in subcutaneous adipose tissue influenced by contractions in adjacent muscles in humans? American Journal of Physiology-Endocrinology and Metabolism, 292(2), 394–399.
di Palumbo A., Guerra E., Orlandi C, Bazzucchi I, Sacchetti M. (2017) Effect of combined resistance and endurance exercise training on regional fat loss. J Sports Med Phys Fitness. 57(6):794-801.
Löberbauer-Purer, E., Meyer, N. L., Ring-Dimitriou, S., Haudum, J., Kässmann, H., & Müller, E. (2011). Can alternating lower body negative and positive pressure during exercise alter regional body fat distribution or skin appearance? European Journal of Applied Physiology, 112(5), 1861–1871.