So here's the thing, having a lot of hair is often referred to as having big hair... thick hair.  However, hair thickness or coarseness, refers to the size of individual strands, while having many (hundreds) of hair strands per square inch refers to density. Therefore, it is possible to have densely packed fine hair strands, in order words you can have "a whole lot" of fine hair strands or not so densely packed thick strands. According to the Science of Black Hair, "a strand of frayed thread is about the thickness of a medium sized strand of hair. If your strand is larger than this, then your hair is thick, if your strand is smaller than this, your hair is fine."
Thicken up the strands you already have to create the illusion of bigger hair, because genetics already determined how many follicles you were gifted.
For the most part, the thickness and density of your hair is determined by genetics and hormones.  It is said that having large follicles yields larger strands and vice versa. So unfortunately, if you were not born with thick/coarse strands, then it is unlikely that there is anything that you can do to "make your strands thicker." However, hair that was once quite dense but thinned due to medication, hormonal issues, chemical treatments or hair color does have the ability to be "re-thickened," so to speak.  For the purposes of this article, we're going to discuss ways to potentially thicken up the strands you already have to create the illusion of bigger hair, as genetics already determined how many follicles you were gifted.

Get your protein

Hair is made up of protein and a break down of the protein structure will cause hair to thin. Incorporating more protein into one's diet as well as adding strengthening protein products (hydrolyzed protein) to your hair will help to fill in any gaps/spaces that may be in the hair shaft, causing it to appear thicker. 
Note: Don't overdo the protein products though because if your hair is not sufficiently "soft AND strong" (protein-moisture balance) you will end up with a whole other set of problems.

Fake it with henna

Henna and cassia  both mimic protein treatments and coat the hair shaft, causing the hair strand to appear thicker. Both of these treatments (especially henna) may loosen your curl pattern overtime, so it's important to take steps (adding Amla powder, spacing treatments and/or doing just your roots) to prevent this if it's not a desired effect. I know this works because I used henna/cassia treatments to re-thicken areas of my hair that thinned a bit due to medication.

Dry styling

Styling on dry hair is a great option for allowing your hair to appear fuller.

Castor oil for thicker hair

Applying  Castor oil  is always the suggestion when someone asks "what can I do to thicken my hair." I know for a fact it works on hair that was once thick since I've used to re-thicken my edges. However, I do not know for sure if it works on "genetically" fine hair. The theory behind Castor oil is that "when rubbed on the scalp, castor oil has restorative properties that not only keep the scalp moisturized, but also help thin hair grow thicker and keep hair from falling out. The Omega-9 fatty acids in castor oil helps to regenerate new hair growth within just a few months."  Source

The only issue with these "solutions" is that they are temporary so they need to be constantly repeated in order to maintain the benefits.

CurlyNikki Says:

Henna works to build up my puny strands.  My strands go from wispy/see-through, to baby doll strands (coarser, fortified and shiny as hell) after a few treatments.  If you decide to embark on a henna journey do your research first!  Styling on dry hair is another trick I lean on in the cooler months.  Works like a charm!  Share your tips below!

What's your take on hair thickness? Have you had any success with hair thickening remedies? 

This post was written by The Hodge Podge Files for CurlyNikki.